Additive and application thereof

ABSTRACT

An additive, liquid-crystal composition and a liquid-crystal display using the additive are provided. The additive includes a first additive molecule having a structure represented by formula (I):wherein Ri1, Ri2, Ri3, Ai1, Ai2, Zi, m1 and m2 are defined as in the specification.

CROSS REFERENCE TO RELATED APPLICATIONS

This Application claims priority of Taiwan Patent Application No.108102903, filed on Jan. 25, 2019, the entirety of which is incorporatedby reference herein.

BACKGROUND Technical Field

The present disclosure relates to an additive, a liquid-crystalcomposition, and a liquid-crystal display device using the additive.

Description of the Related Art

Liquid-crystal display devices have been used in various applications,including personal computers, personal digital assistants (PDAs), mobilephones, televisions, and so on, because these devices have manyadvantages. These advantages include being light in weight, having lowpower consumption, and not emitting radiation.

In a liquid-crystal display device, the alignment of liquid-crystalmolecules can be achieved with a polyimide film. Conventionalliquid-crystal alignment layers are generally produced by coating apolyimide onto a substrate to form a film, and then mechanically rubbingit to form the desired liquid-crystal alignment groove on the surface ofthe polyimide film. However, after rubbing the alignment film, unevenalignment may occur, or serious brush marks may be produced. As aresult, the product yield of the liquid-crystal display device is notgood.

Furthermore, the procedure can also be simplified without an alignmentlayer. Therefore, manufacturers have begun to develop liquid-crystaldisplay devices having no alignment layer. The liquid-crystalcomposition of such a liquid-crystal display device contains polarcompounds, and the liquid-crystal molecules are vertically aligned bythe function of the polar compounds. However, it is difficult for suchpolar compounds to be compatible with vertical alignment ability and ahigh voltage holding ratio. Furthermore, the stability of the alignmentability of such polar compounds also needs to be improved.

Accordingly, a liquid-crystal composition having excellent verticalalignment ability, a high voltage holding ratio, and a high stability ofits alignment ability is still needed in this technical field.

BRIEF SUMMARY

In one embodiment of the present disclosure, an additive is provided.The additive includes a first additive molecule, and the first additivemolecule has a structure represented by formula (I):

wherein, in formula (I),

R^(i1) represents fluorine, chlorine, hydrogen, a C₁-C₂₀ linear alkylgroup, a C₃-C₂₀ branched alkyl group, a C₁-C₂₀ linear alkoxy group, or aC₃-C₂₀ branched alkoxy group, wherein the C₁-C₂₀ linear alkyl group, theC₃-C₂₀ branched alkyl group, the C₁-C₂₀ linear alkoxy group, or theC₃-C₂₀ branched alkoxy group is unsubstituted or at least one —CH₂— ofthe C₁-C₂₀ linear alkyl group, the C₃-C₂₀ branched alkyl group, theC₁-C₂₀ linear alkoxy group, or the C₃-C₂₀ branched alkoxy group issubstituted by —C≡C—, —CH═CH—, —CF₂O—, —O—, —COO—, —OCO—, or —OOC—,and/or at least one hydrogen atom of the C₁-C₂₀ linear alkyl group, theC₃-C₂₀ branched alkyl group, the C₁-C₂₀ linear alkoxy group, or theC₃-C₂₀ branched alkoxy group is substituted by a halogen atom;

A^(i1) represents a 1,4-phenylene group, a 1,4-cyclohexylene group, abenzofuran-2,5-diyl group, a 1,3-dioxane-2,5-diyl group, atetrahydropyran-2,5-diyl group, a divalent dioxabicyclo[2.2.2]octylenegroup, a divalent trioxabicyclo[2.2.2]octylene group, atetrahydronaphthalene-2,6-diyl group, a 1,3-cyclopentylene, a1,3-cyclobutylene, or an indane-2,5-diyl group, wherein the1,4-phenylene group, the 1,4-cyclohexylene group, thetetrahydronaphthalene-2,6-diyl group, the 1,3-cyclopentylene, thebenzofuran-2,5-diyl group, the 1,3-cyclobutylene, or the indane-2,5-diylgroup is unsubstituted or at least one hydrogen atom of the1,4-phenylene group, the 1,4-cyclohexylene group, thetetrahydronaphthalene-2,6-diyl group, the 1,3-cyclopentylene, thebenzofuran-2,5-diyl group, the 1,3-cyclobutylene, or the indane-2,5-diylgroup is substituted by a halogen atom, —CH₃, —CH₂CH₃, or a —CN group,and/or at least one —CH₂— of the 1,4-phenylene group, the1,4-cyclohexylene group, the tetrahydronaphthalene-2,6-diyl group, the1,3-cyclopentylene, the benzofuran-2,5-diyl group, the1,3-cyclobutylene, or the indane-2,5-diyl group is substituted by —O—,—N— or —S—, and wherein the —O—, —N—, and —S— do not directly bond toone another;

A^(i2) represents a 1,4-phenylene group, a 1,4-cyclohexylene group, abenzofuran-2,5-diyl group, a tetrahydronaphthalene-2,6-diyl group, or anindane-2,5-diyl group, wherein the 1,4-phenylene group, the1,4-cyclohexylene group, the tetrahydronaphthalene-2,6-diyl group, thebenzofuran-2,5-diyl group, or the indane-2,5-diyl group is unsubstitutedor at least one hydrogen atom of the 1,4-phenylene group, the1,4-cyclohexylene group, the tetrahydronaphthalene-2,6-diyl group, thebenzofuran-2,5-diyl group, or the indane-2,5-diyl group is substitutedby a halogen atom, —CH₃, —CH₂CH₃, or a —CN group, and/or at least one—CH₂— of the 1,4-phenylene group, the 1,4-cyclohexylene group, thetetrahydronaphthalene-2,6-diyl group, the benzofuran-2,5-diyl group, orthe indane-2,5-diyl group is substituted by —O—, —N— or —S—, and whereinthe —O—, —N—, and —S— do not directly bond to one another;

Z^(i) represents a single bond, a C₁-C₁₅ alkylene group, a C₁-C₅alkyleneoxy group, —C≡C—, —CH═CH—, —CF₂O—, —OCF₂—, —COO—, —OCO—, —OOC—,—CF₂—CF₂—, or —CF═CF—;

m¹ represents 0, 1, 2, 3, or 4, and when m¹ represents 2, 3, or 4, thetwo or more A^(i1) groups are identical to each other or different fromeach other, and the two or more Z^(i) groups are identical to each otheror different from each other;

m² represents 1, 2, or 3, and when m² represents 2 or 3, the two or moreR^(i2) groups are identical to each other or different from each other;

R^(i2) represents a structure represented by formula (Ia), formula (Ib),or formula (Ic), and at least one R^(i2) represents the structurerepresented by formula (Ib) or formula (Ic):

R^(i3) represents a structure represented by formula (Id), formula (Ie),or formula (If):

wherein, in formula (Ia), formula (Ib), formula (Ic), formula (Id),formula (Ie), and formula (If),

A^(i3) represents a 1,4-phenylene group, a 1,4-cyclohexylene group, a1,3-cyclopentylene, or a 1,3-cyclobutylene, wherein the 1,4-phenylenegroup, the 1,4-cyclohexylene group, the 1,3-cyclopentylene, or the1,3-cyclobutylene is unsubstituted or at least one hydrogen atom of the1,4-phenylene group, the 1,4-cyclohexylene group, the1,3-cyclopentylene, or the 1,3-cyclobutylene is substituted by a halogenatom, —CH₃, —CH₂CH₃, or a —CN group, and/or at least one —CH═ of the1,4-phenylene group, the 1,4-cyclohexylene group, the1,3-cyclopentylene, or the 1,3-cyclobutylene is substituted by —N═,and/or at least one —CH₂— of the 1,4-phenylene group, the1,4-cyclohexylene group, the 1,3-cyclopentylene, or the1,3-cyclobutylene is substituted by —O—, —NR^(e)— or —S—, and whereinthe —O—, —NR^(e)—, and —S— do not directly bond to one another, whereinR^(e) represents hydrogen, a C₁-C₄ linear alkyl group, or a C₃-C₄branched alkyl group;

each of R^(i4), R^(i5), and R^(i6) independently represents fluorine,chlorine, hydrogen, a C₁-C₂₀ linear alkyl group, a C₃-C₂₀ branched alkylgroup, a C₁-C₂₀ linear alkoxy group, or a C₃-C₂₀ branched alkoxy group,wherein the C₁-C₂₀ linear alkyl group, the C₃-C₂₀ branched alkyl group,the C₁-C₂₀ linear alkoxy group, or the C₃-C₂₀ branched alkoxy group isunsubstituted or at least one —CH₂— of the C₁-C₂₀ linear alkyl group,the C₃-C₂₀ branched alkyl group, the C₁-C₂₀ linear alkoxy group, or theC₃-C₂₀ branched alkoxy group is substituted by —C≡C—, —CH═CH—, —CF₂O—,—O—, —COO—, —OCO—, or —OOC—, and/or at least one hydrogen atom of theC₁-C₂₀ linear alkyl group, the C₃-C₂₀ branched alkyl group, the C₁-C₂₀linear alkoxy group, or the C₃-C₂₀ branched alkoxy group is substitutedby a halogen atom;

each of L^(i1), L^(i2), L^(i3), L^(i4), L^(i5), L^(i6), L^(i7), L^(i8),L^(i9), and L^(i10) independently represents a single bond, a C₁-C₁₅linear alkylene group, a C₃-C₁₅ branched alkylene group, a C₁-C₁₅ linearalkyleneoxy group, or a C₃-C₁₅ branched alkyleneoxy group, wherein theC₁-C₁₅ linear alkylene group, the C₃-C₁₅ branched alkylene group, theC₁-C₁₅ linear alkyleneoxy group, or the C₃-C₁₅ branched alkyleneoxygroup is unsubstituted or at least one —CH₂— of the C₁-C₁₅ linearalkylene group, the C₃-C₁₅ branched alkylene group, the C₁-C₁₅ linearalkyleneoxy group, or the C₃-C₁₅ branched alkyleneoxy group issubstituted by —C≡C—, —CH═CH—, —CF₂O—, —SiR^(a) ₂—, —O—, —CO—, —COO—,—OCO—, or —OOC—, and/or at least one hydrogen atom of the C₁-C₁₅ linearalkylene group, the C₃-C₁₅ branched alkylene group, the C₁-C₁₅ linearalkyleneoxy group, or the C₃-C₁₅ branched alkyleneoxy group issubstituted by a halogen atom, and wherein R^(a) represents a C₁-C₁₀linear alkyl group or a C₃-C₁₀ branched alkyl group, and two R^(a)groups bonded to the same Si atom are identical to each other ordifferent from each other;

m³ represents 1 or 2, and when m³ represents 2, the two A^(i3) groupsare identical to each other or different from each other, and the twoL^(i3) groups are identical to each other or different from each other;

m⁴ represents 1 or 2, and when m⁴ represents 2, the two A^(i3) groupsare identical to each other or different from each other, and the twoL^(i5) groups are identical to each other or different from each other;

m⁵+m⁶=3, m⁵ represents 2 or 3, and the two or more L^(i6) groups areidentical to each other or different from each other, and the two ormore X^(i3) groups are identical to each other or different from eachother;

m⁷+m⁸=3, m⁷ represents 2 or 3, and the two or more L^(i10) groups areidentical to each other or different from each other, and the two ormore X^(i5) groups are identical to each other or different from eachother;

each of X^(i1), X^(i2), and X^(i3) independently represents hydrogen,—OH,

and

each of X^(i4) and X^(i5) independently represents hydrogen, —OH,

wherein at least one of X^(i1), X^(i2), X^(i3), X^(i4), and X^(i5)represents or

and

wherein Y^(i1) represents —OH, a C₁-C₁₅ alkyl group, or a C₂-C₁₅ alkenylgroup, and at least one hydrogen atom of the C₁-C₁₅ alkyl group or theC₂-C₁₅ alkenyl group is substituted by —OH;

Y^(i2) represents hydrogen, halogen, a C₁-C₁₅ alkyl group, or a C₂-C₁₅alkenyl group, wherein the C₁-C₁₅ alkyl group or the C₂-C₁₅ alkenylgroup is unsubstituted or at least one hydrogen atom of the C₁-C₁₅ alkylgroup or the C₂-C₁₅ alkenyl group is substituted by a halogen atom.

In other embodiments of the present disclosure, a liquid-crystalcomposition is provided. The liquid-crystal composition includes a firstcomponent and a second component. The first component includes at leastone additive as mentioned above, and the second component includes atleast one compound represented by formula (II):

wherein

each of R²¹ and R²² independently represents hydrogen, halogen, a C₁-C₁₅alkyl group, or a C₂-C₁₅ alkenyl group, wherein the C₁-C₁₅ alkyl groupor the C₂-C₁₅ alkenyl group is unsubstituted or at least one hydrogenatom of the C₁-C₁₅ alkyl group or the C₂-C₁₅ alkenyl group issubstituted by a halogen atom, and/or at least one —CH₂— of the C₁-C₁₅alkyl group or the C₂-C₁₅ alkenyl group is substituted by —O—, andwherein the —O— does not directly bond to another —O—;

each of B¹, B², and B³ independently represents a 1,4-phenylene group, a1,4-cyclohexylene group, a benzofuran-2,5-diyl group, a1,3-dioxane-2,5-diyl group, a tetrahydropyran-2,5-diyl group, a divalentdioxabicyclo[2.2.2]octylene group, a divalenttrioxabicyclo[2.2.2]octylene group, a tetrahydronaphthalene-2,6-diylgroup, or an indane-2,5-diyl group, wherein the 1,4-phenylene group, the1,4-cyclohexylene group, the 1,3-dioxane-2,5-diyl group, thebenzofuran-2,5-diyl group, the tetrahydronaphthalene-2,6-diyl group, theindane-2,5-diyl group, or the tetrahydropyran-2,5-diyl group isunsubstituted or at least one hydrogen atom of the 1,4-phenylene group,the 1,4-cyclohexylene group, the 1,3-dioxane-2,5-diyl group, thebenzofuran-2,5-diyl group, the tetrahydronaphthalene-2,6-diyl group, theindane-2,5-diyl group, or the tetrahydropyran-2,5-diyl group issubstituted by a halogen atom or a —CN group, and/or at least one —CH₂—of the 1,4-phenylene group, the 1,4-cyclohexylene group, the1,3-dioxane-2,5-diyl group, the benzofuran-2,5-diyl group, thetetrahydronaphthalene-2,6-diyl group, the indane-2,5-diyl group, or thetetrahydropyran-2,5-diyl group is substituted by —O—, —N— or —S—, andwherein the —O—, —N—, and —S— do not directly bond to one another;

each of Z²¹ and Z²² independently represents a single bond, a C₁-C₄alkylene group, a C₂-C₄ alkenylene group, or a C₂-C₄ alkynylene group,wherein the C₁-C₄ alkylene group, the C₂-C₄ alkenylene group, or theC₂-C₄ alkynylene group is unsubstituted or at least one hydrogen atom ofthe C₁-C₄ alkylene group, the C₂-C₄ alkenylene group, or the C₂-C₄alkynylene group is substituted by a halogen atom or a —CN group, and/orat least one —CH₂— of the C₁-C₄ alkylene group, the C₂-C₄ alkenylenegroup, or the C₂-C₄ alkynylene group is substituted by —O— or —S—, andwherein the —O— does not directly bond to —O— or —S—, and —S— does notdirectly bond to —S—; and

n²¹ represents 0, 1, or 2, and when n²¹ represents 2, the two B¹ groupsare identical to each other or different from each other.

In other embodiments of the present disclosure, a liquid-crystal displaydevice is provided. The liquid-crystal display device includes a firstsubstrate and a second substrate disposed opposite to the firstsubstrate. The liquid-crystal display device also includes aliquid-crystal layer disposed between the first substrate and the secondsubstrate. The liquid-crystal layer includes the above-mentionedadditive.

Embodiments of the present disclosure provide an additive, and aliquid-crystal composition and a liquid-crystal display device using theadditive, which can greatly improve the vertical alignment property,voltage holding ratio, and stability of the alignment ability of theliquid-crystal composition. Therefore, the performance and durability ofthe liquid-crystal display device can be improved.

BRIEF DESCRIPTION OF THE DRAWINGS

To further simplify and clarify the foregoing contents and otherobjects, characteristics, and merits of the present disclosure, adetailed description is given in the following embodiments withreference to the accompanying drawings. It should be emphasized thatmany features are not drawn to scale according to industry standardpractice. In fact, the dimensions of the various components may bearbitrarily increased or decreased for clarity of discussion.

The sole FIGURE is a cross-sectional view showing a liquid-crystaldisplay device in accordance with some embodiments of the presentdisclosure.

DETAILED DESCRIPTION

In the present specification, the term “about” or “approximately” meansin a range of 20% of a given value or range, preferably 10%, and morepreferably 5%. In the present specification, if there is no specificexplanation, a given value or range means an approximate value which mayimply the meaning of “about” or “approximately”.

In the present specification, when two or more functional groups usingthe same code are included in one chemical formula, the two groups maybe identical to each other or different from each other. For example, informula (1), when m¹ is 2, two A^(i1) groups may be identical to eachother or different from each other, and two Z^(i) groups may also beidentical to each other or different from each other. In other words,the description of “two A^(i1) groups and Z^(i) groups are independentlyidentical to each other or different from each other” may include allthe following cases: (1) the two A^(i1) groups are identical to eachother, and the two Z^(i) groups are identical to each other; (2) the twoA^(i1) groups are different from each other, but the two Z^(i) groupsare identical to each other; (3) the two A^(i1) groups are identical toeach other, but the two Z^(i) groups are different from each other; and(4) the two A^(i1) groups are different from each other, and the twoZ^(i) groups are different from each other.

In the present specification, the wavy line is used to indicate the atomto which this functional group is bonded to another functional group.For example, in the functional group

the leftmost oxygen atom is the atom bonded to another functional group.

In some embodiments of the present disclosure, an additive is provided.The additive can greatly improve the vertical alignment degree, voltageholding ratio, and stability of the alignment ability of theliquid-crystal composition. In the present specification, the term“vertical alignment ability of the additive molecule” means the degreeof vertical alignment of liquid-crystal molecules in a liquid-crystalcomposition when the additive is added to the liquid-crystalcomposition. More specifically, by adding the additive molecule to theliquid-crystal composition, most liquid-crystal molecules can bevertically aligned well without using a conventional alignment film (forexample, a polyimide film). Furthermore, the liquid-crystal displaydevice using the additive has a high voltage holding ratio and excellentperformance.

In some embodiments, an additive is provided. The additive includes afirst additive molecule, and the first additive molecule has a structurerepresented by formula (I):

wherein, in formula (I),

R^(i1) represents fluorine, chlorine, hydrogen, a C₁-C₂₀ linear alkylgroup, a C₃-C₂₀ branched alkyl group, a C₁-C₂₀ linear alkoxy group, or aC₃-C₂₀ branched alkoxy group, wherein the C₁-C₂₀ linear alkyl group, theC₃-C₂₀ branched alkyl group, the C₁-C₂₀ linear alkoxy group, or theC₃-C₂₀ branched alkoxy group is unsubstituted or at least one —CH₂— ofthe C₁-C₂₀ linear alkyl group, the C₃-C₂₀ branched alkyl group, theC₁-C₂₀ linear alkoxy group, or the C₃-C₂₀ branched alkoxy group issubstituted by —C≡C—, —CH═CH—, —CF₂O—, —O—, —COO—, —OCO—, or —OOC—,and/or at least one hydrogen atom of the C₁-C₂₀ linear alkyl group, theC₃-C₂₀ branched alkyl group, the C₁-C₂₀ linear alkoxy group, or theC₃-C₂₀ branched alkoxy group is substituted by a halogen atom;

A^(i1) represents a 1,4-phenylene group, a 1,4-cyclohexylene group, abenzofuran-2,5-diyl group, a 1,3-dioxane-2,5-diyl group, atetrahydropyran-2,5-diyl group, a divalent dioxabicyclo[2.2.2]octylenegroup, a divalent trioxabicyclo[2.2.2]octylene group, atetrahydronaphthalene-2,6-diyl group, a 1,3-cyclopentylene, a1,3-cyclobutylene, or an indane-2,5-diyl group, wherein the1,4-phenylene group, the 1,4-cyclohexylene group, thetetrahydronaphthalene-2,6-diyl group, the 1,3-cyclopentylene, thebenzofuran-2,5-diyl group, the 1,3-cyclobutylene, or the indane-2,5-diylgroup is unsubstituted or at least one hydrogen atom of the1,4-phenylene group, the 1,4-cyclohexylene group, thetetrahydronaphthalene-2,6-diyl group, the 1,3-cyclopentylene, thebenzofuran-2,5-diyl group, the 1,3-cyclobutylene, or the indane-2,5-diylgroup is substituted by a halogen atom, —CH₃, —CH₂CH₃, or a —CN group,and/or at least one —CH₂— of the 1,4-phenylene group, the1,4-cyclohexylene group, the tetrahydronaphthalene-2,6-diyl group, the1,3-cyclopentylene, the benzofuran-2,5-diyl group, the1,3-cyclobutylene, or the indane-2,5-diyl group is substituted by —O—,—N— or —S—, and wherein the —O—, —N—, and —S— do not directly bond toone another;

A^(i2) represents a 1,4-phenylene group, a 1,4-cyclohexylene group, abenzofuran-2,5-diyl group, a tetrahydronaphthalene-2,6-diyl group, or anindane-2,5-diyl group, wherein the 1,4-phenylene group, the1,4-cyclohexylene group, the tetrahydronaphthalene-2,6-diyl group, thebenzofuran-2,5-diyl group, or the indane-2,5-diyl group is unsubstitutedor at least one hydrogen atom of the 1,4-phenylene group, the1,4-cyclohexylene group, the tetrahydronaphthalene-2,6-diyl group, thebenzofuran-2,5-diyl group, or the indane-2,5-diyl group is substitutedby a halogen atom, —CH₃, —CH₂CH₃, or a —CN group, and/or at least one—CH₂— of the 1,4-phenylene group, the 1,4-cyclohexylene group, thetetrahydronaphthalene-2,6-diyl group, the benzofuran-2,5-diyl group, orthe indane-2,5-diyl group is substituted by —O—, —N— or —S—, and whereinthe —O—, —N—, and —S— do not directly bond to one another;

Z^(i) represents a single bond, a C₁-C₁₅ alkylene group, a C₁-C₁₅alkyleneoxy group, —C≡C—, —CH═CH—, —CF₂O—, —OCF₂—, —COO—, —OCO—, —OOC—,—CF₂—CF₂—, or —CF═CF—;

m¹ represents 0, 1, 2, 3, or 4, and when m¹ represents 2, 3, or 4, thetwo or more A^(i1) groups are identical to each other or different fromeach other, and the two or more Z^(i) groups are identical to each otheror different from each other;

m² represents 1, 2, or 3, and when m² represents 2 or 3, the two or moreR^(i2) groups are identical to each other or different from each other;

R^(i2) represents a structure represented by formula (Ia), formula (Ib),or formula (Ic), and at least one R^(i2) represents the structurerepresented by formula (Ib) or formula (Ic):

and

R^(i3) represents a structure represented by formula (Id), formula (Ie),or formula (If):

wherein, in formula (Ia), formula (Ib), formula (Ic), formula (Id),formula (Ie), and formula (If),

A^(i3) represents a 1,4-phenylene group, a 1,4-cyclohexylene group, a1,3-cyclopentylene, or a 1,3-cyclobutylene, wherein the 1,4-phenylenegroup, the 1,4-cyclohexylene group, the 1,3-cyclopentylene, or the1,3-cyclobutylene is unsubstituted or at least one hydrogen atom of the1,4-phenylene group, the 1,4-cyclohexylene group, the1,3-cyclopentylene, or the 1,3-cyclobutylene is substituted by a halogenatom, —CH₃, —CH₂CH₃, or a —CN group, and/or at least one —CH═ of the1,4-phenylene group, the 1,4-cyclohexylene group, the1,3-cyclopentylene, or the 1,3-cyclobutylene is substituted by —N═,and/or at least one —CH₂— of the 1,4-phenylene group, the1,4-cyclohexylene group, the 1,3-cyclopentylene, or the1,3-cyclobutylene is substituted by —O—, —NR^(e)— or —S—, and whereinthe —O—, —NR^(e)—, and —S— do not directly bond to one another, whereinR^(e) represents hydrogen, a C₁-C₄ linear alkyl group, or a C₃-C₄branched alkyl group;

each of R^(i4), R^(i5), and R^(i6) independently represents fluorine,chlorine, hydrogen, a C₁-C₂₀ linear alkyl group, a C₃-C₂₀ branched alkylgroup, a C₁-C₂₀ linear alkoxy group, or a C₃-C₂₀ branched alkoxy group,wherein the C₁-C₂₀ linear alkyl group, the C₃-C₂₀ branched alkyl group,the C₁-C₂₀ linear alkoxy group, or the C₃-C₂₀ branched alkoxy group isunsubstituted or at least one —CH₂— of the C₁-C₂₀ linear alkyl group,the C₃-C₂₀ branched alkyl group, the C₁-C₂₀ linear alkoxy group, or theC₃-C₂₀ branched alkoxy group is substituted by —C≡C—, —CH═CH—, —CF₂O—,—O—, —COO—, —OCO—, or —OOC—, and/or at least one hydrogen atom of theC₁-C₂₀ linear alkyl group, the C₃-C₂₀ branched alkyl group, the C₁-C₂₀linear alkoxy group, or the C₃-C₂₀ branched alkoxy group is substitutedby a halogen atom;

each of L^(i1), L^(i2), L^(i3), L^(i4), L^(i5), L^(i6), L^(i7), L^(i8),L^(i9), and L^(i10) independently represents a single bond, a C₁-C₁₅linear alkylene group, a C₃-C₁₅ branched alkylene group, a C₁-C₁₅ linearalkyleneoxy group, or a C₃-C₁₅ branched alkyleneoxy group, wherein theC₁-C₁₅ linear alkylene group, the C₃-C₁₅ branched alkylene group, theC₁-C₁₅ linear alkyleneoxy group, or the C₃-C₁₅ branched alkyleneoxygroup is unsubstituted or at least one —CH₂ of the C₁-C₁₅ linearalkylene group, the C₃-C₁₅ branched alkylene group, the C₁-C₁₅ linearalkyleneoxy group, or the C₃-C₁₅ branched alkyleneoxy group issubstituted by —C≡C—, —CH═CH—, —CF₂O—, —SiR^(a) ₂₋, —O—, —CO—, —COO—,—OCO—, or —OOC—, and/or at least one hydrogen atom of the C₁-C₁₅ linearalkylene group, the C₃-C₁₅ branched alkylene group, the C₁-C₁₅ linearalkyleneoxy group, or the C₃-C₁₅ branched alkyleneoxy group issubstituted by a halogen atom, and wherein R^(a) represents a C₁-C₁₀linear alkyl group or a C₃-C₁₀ branched alkyl group, and two R^(a)groups bonded to the same Si atom are identical to each other ordifferent from each other;

m³ represents 1 or 2, and when m³ represents 2, the two A^(i3) groupsare identical to each other or different from each other, and the twoL^(i3) groups are identical to each other or different from each other;

m⁴ represents 1 or 2, and when m⁴ represents 2, the two A^(i3) groupsare identical to each other or different from each other, and the twoL^(i5) groups are identical to each other or different from each other;

m⁵+m⁶=3, m⁵ represents 2 or 3, and the two or more L^(i6) groups areidentical to each other or different from each other, and the two ormore X^(i3) groups are identical to each other or different from eachother;

m⁷+m=3, m⁷ represents 2 or 3, and the two or more L^(i10) groups areidentical to each other or different from each other, and the two ormore X^(i5) groups are identical to each other or different from eachother;

each of X^(i1), X^(i2), and X^(i3) independently represents hydrogen,—OH,

and

each of X^(i4) and X^(i5) independently represents hydrogen, —OH,

wherein at least one of X^(i1), X^(i2), X^(i3), X^(i4), and X^(i5)represents or

and

wherein Y^(i1) represents —OH, a C₁-C₁₅ alkyl group, or a C₂-C₁₅ alkenylgroup, and at least one hydrogen atom of the C₁-C₁₅ alkyl group or theC₂-C₁₅ alkenyl group is substituted by —OH;

Y^(i2) represents hydrogen, halogen, a C₁-C₁₅ alkyl group, or a C₂-C₁₅alkenyl group, wherein the C₁-C₁₅ alkyl group or the C₂-C₁₅ alkenylgroup is unsubstituted or at least one hydrogen atom of the C₁-C₁₅ alkylgroup or the C₂-C₁₅ alkenyl group is substituted by a halogen atom.

In other embodiments, the above additive includes a first additivemolecule, and the first additive molecule has a structure represented byformula (I′):

wherein, in formula (I′),

R^(i1) represents fluorine, chlorine, hydrogen, a C₁-C₁₂ linear alkylgroup, a C₃-C₁₂ branched alkyl group, a C₁-C₁₂ linear alkoxy group, or aC₃-C₁₂ branched alkoxy group, wherein the C₁-C₁₂ linear alkyl group, theC₃-C₁₂ branched alkyl group, the C₁-C₁₂ linear alkoxy group, or theC₃-C₁₂ branched alkoxy group is unsubstituted or at least one —CH₂— ofthe C₁-C₁₂ linear alkyl group, the C₃-C₁₂ branched alkyl group, theC₁-C₁₂ linear alkoxy group, or the C₃-C₁₂ branched alkoxy group issubstituted by —C≡C—, —CH═CH—, —CF₂O—, —O—, —COO—, —OCO—, or —OOC—,and/or at least one hydrogen atom of the C₁-C₁₂ linear alkyl group, theC₃-C₁₂ branched alkyl group, the C₁-C₁₂ linear alkoxy group, or theC₃-C₁₂ branched alkoxy group is substituted by a halogen atom;

the definitions of A^(i1) and Z^(i) are respectively the same as thedefinitions of A^(i1) and Z^(i) defined in the previous paragraphs; and

m¹ represents 0, 1, 2, 3, or 4, and when m¹ represents 2, 3, or 4, thetwo or more A^(i1) groups are identical to each other or different fromeach other, and the two or more Z^(i) groups are identical to each otheror different from each other;

R^(i2) represents a structure represented by formula (Ia), formula (Ib),or formula (Ic), and at least one R^(i2) represents the structurerepresented by formula (Ib) or formula (Ic):

R^(i3) represents a structure represented by formula (Id), formula (Ie),or formula (If):

wherein, in formula (Ia), formula (Ib), formula (Ic), formula (Id),formula (Ie), and formula (If),

each of R^(i4), R^(i5), and R^(i6) independently represents fluorine,chlorine, hydrogen, a C₁-C₁₂ linear alkyl group, a C₃-C₁₂ branched alkylgroup, a C₁-C₁₂ linear alkoxy group, or a C₃-C₁₂ branched alkoxy group,wherein the C₁-C₁₂ linear alkyl group, the C₃-C₁₂ branched alkyl group,the C₁-C₁₂ linear alkoxy group, or the C₃-C₁₂ branched alkoxy group isunsubstituted or at least one —CH₂— of the C₁-C₁₂ linear alkyl group,the C₃-C₁₂ branched alkyl group, the C₁-C₁₂ linear alkoxy group, or theC₃-C₁₂ branched alkoxy group is substituted by —C≡C—, —CH═CH—, —CF₂O—,—O—, —COO—, —OCO—, or —OOC—, and/or at least one hydrogen atom of theC₁-C₁₂ linear alkyl group, the C₃-C₁₂ branched alkyl group, the C₁-C₁₂linear alkoxy group, or the C₃-C₁₂ branched alkoxy group is substitutedby a halogen atom;

the definitions of L^(i1), L^(i2), L^(i3), L^(i4), L^(i5), L^(i6),L^(i7), L^(i8), L^(i9), L^(i10), A^(i3), m³, m⁴, m⁵, m⁶, m⁷, and m⁸ arerespectively the same as the definitions of, L^(i1), L^(i2), L^(i3),L^(i4), L^(i5), L^(i6), L^(i7), L^(i8), L^(i9), L^(i10), A^(i3), m³, m⁴,m⁵, m⁶, m⁷, and m⁸ defined in the previous paragraphs;

each of X^(i1), X^(i2), X^(i3), X^(i4) and X^(i5) independentlyrepresents hydrogen, —OH,

wherein at least one of X^(i1), X^(i2), X^(i3), X^(i4), and X^(i5)represents

and

wherein Y^(i1) represents —OH, a C₁-C₁₀ alkyl group, or a C₂-C₁₀ alkenylgroup, and at least one hydrogen atom of the C₁-C₁₀ alkyl group or theC₂-C₁₀ alkenyl group is substituted by —OH;

Y^(i2) represents hydrogen, halogen, a C₁-C₁₀ alkyl group, or a C₂-C₁₀alkenyl group, wherein the C₁-C₁₀ alkyl group or the C₂-C₁₀ alkenylgroup is unsubstituted or at least one hydrogen atom of the C₁-C₁₀ alkylgroup or the C₂-C₁₀ alkenyl group is substituted by a halogen atom.

The structure represented by formula (I) or formula (I′) issubstantially a rod-shaped structure. This rod-shaped structure has afirst axial direction and a second axial direction. The first axialdirection is substantially the long axial direction of the rod-shapedstructure, that is, the direction in which the functional group R^(i1)and the functional group R^(i3) are connected. The second axialdirection is the short axial direction of the rod-shaped structure, thatis, a direction perpendicular to the first axial direction.

In some embodiments, in the above formula (I) or formula (I′), at leastone of the functional groups X^(i1), X^(i2), X^(i3), X^(i4), and X^(i5)may include an anchoring group. In such embodiments, the first additivemolecules can be fixed to the substrate (for example, the firstsubstrate 110 or the second substrate 120 shown in the FIGURE). In otherembodiments, in the above formula (I) or formula (I′), all of thefunctional groups X^(i1), X^(i2), X^(i3), X^(i4), and X^(i5) do notinclude anchor groups. In such embodiments, the first additive moleculemay be used together with other additive molecules (for example, asecond additive molecule or a third additive molecule described later)having an anchor group and a polymerizable group.

The anchoring group may be a functional group having a higher polarity.The anchoring group may generate a bond or a hydrogen bond with asubstrate (for example, glass or ITO), and therefore, the first additivemolecules can be adsorbed (or fixed) on the substrate. For example, theanchoring group may include —OH,

In order to achieve a state in which the liquid-crystal molecules arewell aligned vertically, the first additive molecules may be fixed onthe substrate in such a manner that the first axial direction isperpendicular to the top surface of the substrate. In some embodiments,the anchoring group is one of X^(i1), X^(i2), X^(i3), X^(i4), and X^(i5)that is closest to the right end of the molecule represented by formula(I) or formula (I′) such that the first axis is perpendicular to the topsurface of the substrate.

In the above formula (I) or formula (I′), the cyclic functional groupA^(i2) bonded to the functional group R^(i3) may have at least one sidechain functional group R^(i2). One end of the side chain functionalgroup R^(i2) is bonded to the cyclic functional group A^(i2), and theother end of the side chain functional group R^(i2) may include apolymerizable group. The polymerizable group may undergo thepolymerization reaction with another polymerizable group by irradiationor heating, and the two polymerizable groups may be bonded to eachother. When a plurality of additive molecules are fixed on thesubstrate, the polymerizable group of the additive molecule undergoesthe polymerization reaction with the polymerizable group of the adjacentadditive molecule. In this way, a plurality of the additive moleculesthat are perpendicular to the substrate and arranged in parallel witheach other can form a network structure. This network structure canavoid the tilt of the additive molecules. As a result, the degree ofvertical alignment of the liquid-crystal molecules is further improved,and the stability of the alignment ability is also improved.Furthermore, if the additive molecule has an OH functional group, theadditive molecule in the liquid-crystal composition may become freestate when a voltage is applied. This will reduce the voltage holdingratio. In such a case, if this additive molecule is polymerized withother additive molecules through the polymerizable group, the additivecan be prevented from becoming free state when a voltage is applied. Asa result, the voltage holding ratio can be increased. The polymerizablegroup may include an acrylic group, a methacrylic group, or a derivativethereof. In some embodiments, at least one of the functional groupsX^(i1), X^(i2), X^(i3), X^(i4), and X^(i5) is a polymerizable grouphaving the following structure:

wherein Y^(i1) represents —OH, a C₁-C₁₅ alkyl group, or a C₂-C₁₅ alkenylgroup, and at least one hydrogen atom of the C₁-C₁₅ alkyl group or theC₂-C₁₅ alkenyl group is substituted by —OH; and Y^(i2) representshydrogen, halogen, a C₁-C₁₅ alkyl group, or a C₂-C₁₅ alkenyl group,wherein the C₁-C₁₅ alkyl group or the C₂-C₁₅ alkenyl group isunsubstituted or at least one hydrogen atom of the C₁-C₁₅ alkyl group orthe C₂-C₁₅ alkenyl group is substituted by a halogen atom.

In the above formula (I) or formula (I′), the side chain functionalgroup R^(i2) may include at least one cyclic functional group A^(i3).The cyclic functional group A^(i3) can increase the rigidity of the sidechain functional group R^(i2), and it is advantageous for improving thestability of the alignment ability of the liquid-crystal molecules. Morespecifically, when the above network structure is formed, the side chainfunctional group R^(i2) can maintain a specific distance betweenadjacent additive molecules. If the rigidity of the side chainfunctional group R^(i2) is higher, the difference (or the degree ofvariance) of this specific distance between different additive moleculesis smaller. In other words, in the formed network structure, thedistance between adjacent additive molecules is fixed and uniform. As aresult, the stability of the alignment ability of the liquid-crystalmolecules can be greatly improved.

The cyclic functional group A^(i3) may be an aromatic ring, an aliphaticring, or a combination thereof. In some embodiments, all of the cyclicfunctional groups A^(i3) are aromatic rings, so that the side chainfunctional group R^(i2) can have higher rigidity. In other embodiments,all of the cyclic functional groups A^(i3) are aliphatic rings, so thatthe solubility of the additive molecules in the liquid-crystalcomposition can be better. In still other embodiments, some of thecyclic functional groups A^(i3) are aliphatic rings, and the remainingcyclic functional groups A^(i3) are aromatic rings. In such embodiments,the solubility of the additive molecules and the stability of thealignment ability can be respectively adjusted to the required ranges byadjusting the cyclic functional group A^(i3).

In some embodiments, the first additive molecule includes one side chainfunctional group R^(i2). In other embodiments, the first additivemolecule includes two side chain functional groups R^(i2), and the twoside chain functional groups R^(i2) are respectively disposed onopposite sides of the cyclic functional group A^(i2). For example, insome embodiments, the cyclic functional group A^(i2) is a six-memberedring, and the main chain functional groups Z^(i) and R^(i3) are disposedon the first and fourth carbon atoms, respectively. In such anembodiment, the positions of the two side chain functional groups R^(i2)may include all of the following situations: (1) the two side chainfunctional groups R^(i2) are disposed on the second and fifth carbonatoms, respectively; (2) the two side chain functional groups R^(i2) aredisposed on the second and sixth carbon atoms, respectively; (3) the twoside chain functional groups R^(i2) are disposed on the third and fifthcarbon atoms, respectively; and (4) the two side chain functional groupsR^(i2) are disposed on the third and sixth carbon atoms, respectively.In this way, the stability of the alignment ability of theliquid-crystal molecules can be further improved.

As described above, the structure represented by formula (I) or formula(I′) is substantially a rod-shaped structure, and the rod-shapedstructure has a first axial direction and a second axial direction. Ifthe molecular chain length in the first axial direction is longer thanthe molecular chain length in the second axial direction, the additivemolecules can have better vertical alignment ability. Therefore, themolecular chain length of each side chain functional group R^(i2) may bemade shorter than that of the main chain (i.e., the total length of themolecular chain from the functional group R^(i1) to the functional groupR^(i3)).

In some embodiments, the above-mentioned additive further includes asecond additive molecule, and the second additive molecule has astructure represented by formula (I-1):

wherein, in formula (I-1),

R¹ represents fluorine, chlorine, hydrogen, a C₁-C₁₅ linear alkyl group,a C₃-C₁₅ branched alkyl group, a C₁-C₁₅ linear alkoxy group, or a C₃-C₁₅branched alkoxy group, wherein the C₁-C₁₅ linear alkyl group, the C₃-C₁₅branched alkyl group, the C₁-C₁₅ linear alkoxy group, or the C₃-C₁₅branched alkoxy group is unsubstituted or at least one —CH₂— of theC₁-C₁₅ linear alkyl group, the C₃-C₁₅ branched alkyl group, the C₁-C₁₅linear alkoxy group, or the C₃-C₁₅ branched alkoxy group is substitutedby —CH═CH—, —CF₂O—, —O—, —COO—, —OCO—, or —OOC—, and/or at least onehydrogen atom of the C₁-C₁₅ linear alkyl group, the C₃-C₁₅ branchedalkyl group, the C₁-C₁₅ linear alkoxy group, or the C₃-C₁₅ branchedalkoxy group is substituted by a halogen atom;

A¹ represents a 1,4-phenylene group, a 1,4-cyclohexylene group, abenzofuran-2,5-diyl group, a 1,3-dioxane-2,5-diyl group, atetrahydropyran-2,5-diyl group, a divalent dioxabicyclo[2.2.2]octylenegroup, a divalent trioxabicyclo[2.2.2]octylene group, atetrahydronaphthalene-2,6-diyl group, a 1,3-cyclopentylene, a1,3-cyclobutylene, or an indane-2,5-diyl group, wherein the1,4-phenylene group, the 1,4-cyclohexylene group, thetetrahydronaphthalene-2,6-diyl group, the 1,3-cyclopentylene, the1,3-cyclobutylene, or the indane-2,5-diyl group is unsubstituted or atleast one hydrogen atom of the 1,4-phenylene group, the1,4-cyclohexylene group, the tetrahydronaphthalene-2,6-diyl group, the1,3-cyclopentylene, the 1,3-cyclobutylene, or the indane-2,5-diyl groupis substituted by a halogen atom, —CH₃, —CH₂CH₃, or a —CN group, and/orat least one —CH₂— of the 1,4-phenylene group, the 1,4-cyclohexylenegroup, the tetrahydronaphthalene-2,6-diyl group, the 1,3-cyclopentylene,the 1,3-cyclobutylene, or the indane-2,5-diyl group is substituted by—O—, —N— or —S—, and wherein the —O—, —N—, and —S— do not directly bondto one another;

A² represents a 1,4-phenylene group, a 1,4-cyclohexylene group, abenzofuran-2,5-diyl group, or an indane-2,5-diyl group, wherein the1,4-phenylene group, the 1,4-cyclohexylene group, thebenzofuran-2,5-diyl group, or the indane-2,5-diyl group is unsubstitutedor at least one hydrogen atom of the 1,4-phenylene group, the1,4-cyclohexylene group, the benzofuran-2,5-diyl group, or theindane-2,5-diyl group is substituted by a halogen atom, —CH₃, —CH₂CH₃,or a —CN group, and/or at least one —CH₂— of the 1,4-phenylene group,the 1,4-cyclohexylene group, the benzofuran-2,5-diyl group, or theindane-2,5-diyl group is substituted by —O—, —N— or —S—, and wherein the—O—, —N—, and —S— do not directly bond to one another;

Z¹ represents a single bond, a C₁-C₁₅ alkylene group, a C₁-C₁₅alkyleneoxy group, —C≡C—, —CH═CH—, —CF₂O—, —OCF₂—, —COO—, —OCO—, —OOC—,—CF₂—CF₂—, or —CF═CF—;

n¹ represents 1, 2, or 3, and when n¹ represents 2 or 3, the two or moreA¹ groups are identical to each other or different from each other, andthe two or more Z¹ groups are identical to each other or different fromeach other;

n² represents 0 or 1; and

K¹ represents a structure represented by formula (I-1-a), formula(I-1-b), or formula (I-1-c):

wherein, in formula (I-1-a), formula (I-1-b), and formula (I-1-c),

each of L² and L³ independently represents a single bond, a C₁-C₁₅linear alkylene group, a C₃-C₁₅ branched alkylene group, a C₁-C₁₅ linearalkyleneoxy group, or a C₃-C₁₅ branched alkyleneoxy group, wherein theC₁-C₁₅ linear alkylene group, the C₃-C₁₅ branched alkylene group, theC₁-C₁₅ linear alkyleneoxy group, or the C₃-C₁₅ branched alkyleneoxygroup is unsubstituted or at least one —CH₂— of the C₁-C₁₅ linearalkylene group, the C₃-C₁₅ branched alkylene group, the C₁-C₁₅ linearalkyleneoxy group, or the C₃-C₁₅ branched alkyleneoxy group issubstituted by —C≡C—, —CH═CH—, —CF₂O—, —SiR^(a) ₂—, —O—, —COO—, —OCO—,or —OOC—, and/or at least one hydrogen atom of the C₁-C₁₅ linearalkylene group, the C₃-C₁₅ branched alkylene group, the C₁-C₁₅ linearalkyleneoxy group, or the C₃-C₁₅ branched alkyleneoxy group issubstituted by a halogen atom, and wherein R^(a) represents a C₁-C₁₀linear alkyl group or a C₃-C₁₀ branched alkyl group, and two R^(a)groups bonded to the same Si atom are identical to each other ordifferent from each other;

each of R², R³ and R⁴ independently represents fluorine, chlorine,hydrogen, a C₁-C₈ linear alkyl group, a C₃-C₈ branched alkyl group, aC₁-C₈ linear alkoxy group, or a C₃-C₈ branched alkoxy group, wherein theC₁-C₈ linear alkyl group, the C₃-C₈ branched alkyl group, the C₁-C₈linear alkoxy group, or the C₃-C₈ branched alkoxy group is unsubstitutedor at least one —CH₂— of the C₁-C₈ linear alkyl group, the C₃-C₈branched alkyl group, the C₁-C₈ linear alkoxy group, or the C₃-C₈branched alkoxy group is substituted by —CH═CH—, —CF₂O—, —O—, —COO—,—OCO—, or —OOC—, and/or at least one hydrogen atom of the C₁-C₈ linearalkyl group, the C₃-C₈ branched alkyl group, the C₁-C₈ linear alkoxygroup, or the C₃-C₈ branched alkoxy group is substituted by a halogenatom;

n³+n⁴=3, n⁴ represents 2 or 3, and the two or more L² groups areidentical to each other or different from each other, and the two ormore X¹ groups are identical to each other or different from each other;

n⁵+n⁶=3, n⁶ represents 2 or 3, and the two or more L² groups areidentical to each other or different from each other, and the two ormore X² groups are identical to each other or different from each other;

each of X¹ and X² independently represents or

wherein Y¹ represents —OH, a C₁-C₈ alkyl group, or a C₂-C₈ alkenylgroup, and at least one hydrogen atom of the C₁-C₈ alkyl group or theC₂-C₈ alkenyl group is substituted by —OH;

Y² represents hydrogen, halogen, a C₁-C₈ alkyl group, or a C₂-C₈ alkenylgroup, wherein the C₁-C₈ alkyl group or the C₂-C₈ alkenyl group isunsubstituted or at least one hydrogen atom of the C₁-C₈ alkyl group orthe C₂-C₈ alkenyl group is substituted by a halogen atom;

K² represents a structure represented by formula (I-1-d), formula(I-1-e), or formula (I-1-f):

and

K³ represents a structure represented by formula (I-1-g) or formula(I-1-h):

wherein, in formula (I-1-d), formula (I-1-e), formula (I-1-f), formula(I-1-g), and formula (I-1-h),

each of L¹, L², L³, L⁴, L⁵, L⁶, and L⁷ independently represents a singlebond, a C₁-C₁₅ linear alkylene group, a C₃-C₁₅ branched alkylene group,a C₁-C₁₅ linear alkyleneoxy group, or a C₃-C₁₅ branched alkyleneoxygroup, wherein the C₁-C₁₅ linear alkylene group, the C₃-C₁₅ branchedalkylene group, the C₁-C₁₅ linear alkyleneoxy group, or the C₃-C₁₅branched alkyleneoxy group is unsubstituted or at least one —CH₂— of theC₁-C₁₅ linear alkylene group, the C₃-C₁₅ branched alkylene group, theC₁-C₁₅ linear alkyleneoxy group, or the C₃-C₁₅ branched alkyleneoxygroup is substituted by —C≡C—, —CH═CH—, —CF₂O—, —SiR^(a) ₂—, —O—, —COO—,—OCO—, or —OOC—, and/or at least one hydrogen atom of the C₁-C₁₅ linearalkylene group, the C₃-C₁₅ branched alkylene group, the C₁-C₁₅ linearalkyleneoxy group, or the C₃-C₁₅ branched alkyleneoxy group issubstituted by a halogen atom, and wherein R^(a) represents a C₁-C₁₀linear alkyl group or a C₃-C₁₀ branched alkyl group, and two R^(a)groups bonded to the same Si atom are identical to each other ordifferent from each other;

each of R², R³, R⁴, R⁵ and R⁶ independently represents fluorine,chlorine, hydrogen, a C₁-C₁₀ linear alkyl group, a C₃-C₁₀ branched alkylgroup, a C₁-C₁₀ linear alkoxy group, or a C₃-C₁₀ branched alkoxy group,wherein the C₁-C₁₀ linear alkyl group, the C₃-C₁₀ branched alkyl group,the C₁-C₁₀ linear alkoxy group, or the C₃-C₁₀ branched alkoxy group isunsubstituted or at least one —CH₂— of the C₁-C₁₀ linear alkyl group,the C₃-C₁₀ branched alkyl group, the C₁-C₁₀ linear alkoxy group, or theC₃-C₁₀ branched alkoxy group is substituted by —C≡C—, —CH═CH—, —CF₂O—,—O—, —COO—, —OCO—, or —OOC—, and/or at least one hydrogen atom of theC₁-C₁₀ linear alkyl group, the C₃-C₁₀ branched alkyl group, the C₁-C₁₀linear alkoxy group, or the C₃-C₁₀ branched alkoxy group is substitutedby a halogen atom;

n⁹+n¹⁰=3, n¹⁰ represents 2 or 3, and the two or more L⁷ groups areidentical to each other or different from each other, and the two ormore X⁴ groups are identical to each other or different from each other;

n¹² represents 1, 2, or 3, n¹¹+n¹²=3, and when n¹² represents 2 or 3,the two or more L² groups are identical to each other or different fromeach other, and the two or more X⁵ groups are identical to each other ordifferent from each other; when n¹¹ represents 2, the two R² groups areidentical to each other or different from each other; and

n¹⁴ represents 1, 2, or 3, n¹³+n¹⁴=3, and when n¹⁴ represents 2 or 3,the two or more L² groups are identical to each other or different fromeach other, and the two or more X⁶ groups are identical to each other ordifferent from each other; when n¹³ represents 2, the two R⁴ groups areidentical to each other or different from each other;

each of X³, X⁴, X⁵ and X⁶ independently represents hydrogen, —OH,

wherein, when K¹ represents the structure represented by formula (I-1-a)or formula (I-1-b), at least one of X¹ and X² represents

when K¹ represents the structure represented by formula (I-1-c), and K²represents the structure represented by formula (I-1-d), at least one ofX⁵ and X⁶ represents

and

when K¹ represents the structure represented by formula (I-1-c), and K²represents the structure represented by formula (I-1-e) or formula(I-1-f), at least one of X³, X⁴, X⁵ and X⁶ represents

In some embodiments, the above-mentioned additive further includes athird additive molecule, and the third additive molecule has a structurerepresented by formula (I-1):

wherein, in formula (I-1),

R¹ represents fluorine, chlorine, hydrogen, a C₁-C₁₅ linear alkyl group,a C₃-C₁₅ branched alkyl group, a C₁-C₁₅ linear alkoxy group, or a C₃-C₁₅branched alkoxy group, wherein the C₁-C₁₅ linear alkyl group, the C₃-C₁₅branched alkyl group, the C₁-C₁₅ linear alkoxy group, or the C₃-C₁₅branched alkoxy group is unsubstituted or at least one —CH₂— of theC₁-C₁₅ linear alkyl group, the C₃-C₁₅ branched alkyl group, the C₁-C₁₅linear alkoxy group, or the C₃-C₁₅ branched alkoxy group is substitutedby —CH═CH—, —CF₂O—, —O—, —COO—, —OCO—, or —OOC—, and/or at least onehydrogen atom of the C₁-C₁₅ linear alkyl group, the C₃-C₁₅ branchedalkyl group, the C₁-C₁₅ linear alkoxy group, or the C₃-C₁₅ branchedalkoxy group is substituted by a halogen atom;

A¹ represents a 1,4-phenylene group, a 1,4-cyclohexylene group, abenzofuran-2,5-diyl group, a 1,3-dioxane-2,5-diyl group, atetrahydropyran-2,5-diyl group, a divalent dioxabicyclo[2.2.2]octylenegroup, a divalent trioxabicyclo[2.2.2]octylene group, atetrahydronaphthalene-2,6-diyl group, a 1,3-cyclopentylene, a1,3-cyclobutylene, or an indane-2,5-diyl group, wherein the1,4-phenylene group, the 1,4-cyclohexylene group, thetetrahydronaphthalene-2,6-diyl group, the 1,3-cyclopentylene, the1,3-cyclobutylene, or the indane-2,5-diyl group is unsubstituted or atleast one hydrogen atom of the 1,4-phenylene group, the1,4-cyclohexylene group, the tetrahydronaphthalene-2,6-diyl group, the1,3-cyclopentylene, the 1,3-cyclobutylene, or the indane-2,5-diyl groupis substituted by a halogen atom, —CH₃, —CH₂CH₃, or a —CN group, and/orat least one —CH₂— of the 1,4-phenylene group, the 1,4-cyclohexylenegroup, the tetrahydronaphthalene-2,6-diyl group, the 1,3-cyclopentylene,the 1,3-cyclobutylene, or the indane-2,5-diyl group is substituted by—O—, —N— or —S—, and wherein the —O—, —N—, and —S— do not directly bondto one another;

A² represents a 1,4-phenylene group, a 1,4-cyclohexylene group, abenzofuran-2,5-diyl group, or an indane-2,5-diyl group, wherein the1,4-phenylene group, the 1,4-cyclohexylene group, thebenzofuran-2,5-diyl group, or the indane-2,5-diyl group is unsubstitutedor at least one hydrogen atom of the 1,4-phenylene group, the1,4-cyclohexylene group, the benzofuran-2,5-diyl group, or theindane-2,5-diyl group is substituted by a halogen atom, —CH₃, —CH₂CH₃,or a —CN group, and/or at least one —CH₂— of the 1,4-phenylene group,the 1,4-cyclohexylene group, the benzofuran-2,5-diyl group, or theindane-2,5-diyl group is substituted by —O—, —N— or —S—, and wherein the—O—, —N—, and —S— do not directly bond to one another;

Z¹ represents a single bond, a C₁-C₁₅ alkylene group, a C₁-C₁₅alkyleneoxy group, —C≡C—, —CH═CH—, —CF₂O—, —OCF₂—, —COO—, —OCO—, —OOC—,—CF₂—CF₂—, or —CF═CF—;

n¹ represents 1, 2, or 3, and when n¹ represents 2 or 3, the two or moreA¹ groups are identical to each other or different from each other, andthe two or more Z¹ groups are identical to each other or different fromeach other;

n² represents 0 or 1; and

K¹ represents a structure represented by formula (I-1-a), formula(I-1-b), or formula (I-1-c):

wherein, in formula (I-1-a), formula (I-1-b), and formula (I-1-c),

each of L² and L³ independently represents a single bond, a C₁-C₁₅linear alkylene group, a C₃-C₁₅ branched alkylene group, a C₁-C₁₅ linearalkyleneoxy group, or a C₃-C₁₅ branched alkyleneoxy group, wherein theC₁-C₁₅ linear alkylene group, the C₃-C₁₅ branched alkylene group, theC₁-C₁₅ linear alkyleneoxy group, or the C₃-C₁₅ branched alkyleneoxygroup is unsubstituted or at least one —CH₂— of the C₁-C₁₅ linearalkylene group, the C₃-C₁₅ branched alkylene group, the C₁-C₁₅ linearalkyleneoxy group, or the C₃-C₁₅ branched alkyleneoxy group issubstituted by —C≡C—, —CH═CH—, —CF₂O—, —SiR^(a) ₂—, —O—, —COO—, —OCO—,or —OOC—, and/or at least one hydrogen atom of the C₁-C₁₅ linearalkylene group, the C₃-C₁₅ branched alkylene group, the C₁-C₁₅ linearalkyleneoxy group, or the C₃-C₁₅ branched alkyleneoxy group issubstituted by a halogen atom, and wherein R^(a) represents a C₁-C₁₀linear alkyl group or a C₃-C₁₀ branched alkyl group, and two R^(a)groups bonded to the same Si atom are identical to each other ordifferent from each other;

each of R², R³ and R⁴ independently represents fluorine, chlorine,hydrogen, a C₁-C₈ linear alkyl group, a C₃-C₈ branched alkyl group, aC₁-C₈ linear alkoxy group, or a C₃-C₈ branched alkoxy group, wherein theC₁-C₈ linear alkyl group, the C₃-C₈ branched alkyl group, the C₁-C₈linear alkoxy group, or the C₃-C₈ branched alkoxy group is unsubstitutedor at least one —CH₂— of the C₁-C₈ linear alkyl group, the C₃-C₈branched alkyl group, the C₁-C₈ linear alkoxy group, or the C₃-C₈branched alkoxy group is substituted by —CH═CH—, —CF₂O—, —O—, —COO—,—OCO—, or —OOC—, and/or at least one hydrogen atom of the C₁-C₈ linearalkyl group, the C₃-C₈ branched alkyl group, the C₁-C₈ linear alkoxygroup, or the C₃-C₈ branched alkoxy group is substituted by a halogenatom;

n³+n⁴=3, n⁴ represents 2 or 3, and the two or more L² groups areidentical to each other or different from each other, and the two ormore X¹ groups are identical to each other or different from each other;

n⁵+n⁶=3, n⁶ represents 2 or 3, and the two or more L² groups areidentical to each other or different from each other, and the two ormore X² groups are identical to each other or different from each other;

each of X¹ and X² independently represents

wherein Y¹ represents —OH, a C₁-C₈ alkyl group, or a C₂-C₈ alkenylgroup, and at least one hydrogen atom of the C₁-C₅ alkyl group or theC₂-C₈ alkenyl group is substituted by —OH;

Y² represents hydrogen, halogen, a C₁-C₈ alkyl group, or a C₂-C₈ alkenylgroup, wherein the C₁-C₈ alkyl group or the C₂-C₈ alkenyl group isunsubstituted or at least one hydrogen atom of the C₁-C₈ alkyl group orthe C₂-C₈ alkenyl group is substituted by a halogen atom;

K² represents a structure represented by formula (I-1-d), formula(I-1-e), or formula (I-1-f):

and

K³ represents a structure represented by formula (I-1-g) or formula(I-1-h):

wherein, in formula (I-1-d), formula (I-1-e), formula (I-1-f), formula(I-1-g), and formula (I-1-h),

each of L¹, L², L³, L⁴, L⁵, L⁶, and L⁷ independently represents a singlebond, a C₁-C₁₅ linear alkylene group, a C₃-C₁₅ branched alkylene group,a C₁-C₁₅ linear alkyleneoxy group, or a C₃-C₁₅ branched alkyleneoxygroup, wherein the C₁-C₁₅ linear alkylene group, the C₃-C₁₅ branchedalkylene group, the C₁-C₁₅ linear alkyleneoxy group, or the C₃-C₁₅branched alkyleneoxy group is unsubstituted or at least one —CH₂— of theC₁-C₁₅ linear alkylene group, the C₃-C₁₅ branched alkylene group, theC₁-C₁₅ linear alkyleneoxy group, or the C₃-C₁₅ branched alkyleneoxygroup is substituted by —C≡C—, —CH═CH—, —CF₂O—, —SiR^(a) ₂—, —O—, —COO—,—OCO—, or —OOC—, and/or at least one hydrogen atom of the C₁-C₁₅ linearalkylene group, the C₃-C₁₅ branched alkylene group, the C₁-C₁₅ linearalkyleneoxy group, or the C₃-C₁₅ branched alkyleneoxy group issubstituted by a halogen atom, and wherein R^(a) represents a C₁-C₁₀linear alkyl group or a C₃-C₁₀ branched alkyl group, and two R^(a)groups bonded to the same Si atom are identical to each other ordifferent from each other;

each of R², R³, R⁴, R⁵ and R⁶ independently represents fluorine,chlorine, hydrogen, a C₁-C₁₀ linear alkyl group, a C₃-C₁₀ branched alkylgroup, a C₁-C₁₀ linear alkoxy group, or a C₃-C₁₀ branched alkoxy group,wherein the C₁-C₁₀ linear alkyl group, the C₃-C₁₀ branched alkyl group,the C₁-C₁₀ linear alkoxy group, or the C₃-C₁₀ branched alkoxy group isunsubstituted or at least one —CH₂— of the C₁-C₁₀ linear alkyl group,the C₃-C₁₀ branched alkyl group, the C₁-C₁₀ linear alkoxy group, or theC₃-C₁₀ branched alkoxy group is substituted by —C≡C—, —CH═CH—, —CF₂O—,—O—, —COO—, —OCO—, or —OOC—, and/or at least one hydrogen atom of theC₁-C₁₀ linear alkyl group, the C₃-C₁₀ branched alkyl group, the C₁-C₁₀linear alkoxy group, or the C₃-C₁₀ branched alkoxy group is substitutedby a halogen atom;

n⁹+n¹⁰=3, n¹⁰ represents 2 or 3, and the two or more L⁷ groups areidentical to each other or different from each other, and the two ormore X⁴ groups are identical to each other or different from each other;

n¹² represents 1, 2, or 3, n¹¹+n¹²=3, and when n¹² represents 2 or 3,the two or more L² groups are identical to each other or different fromeach other, and the two or more X⁵ groups are identical to each other ordifferent from each other; when n¹¹ represents 2, the two R² groups areidentical to each other or different from each other; and

n¹⁴ represents 1, 2, or 3, n¹³+n¹⁴=3, and when n¹⁴ represents 2 or 3,the two or more L² groups are identical to each other or different fromeach other, and the two or more X⁶ groups are identical to each other ordifferent from each other; when n¹³ represents 2, the two R⁴ groups areidentical to each other or different from each other;

each of X³, X⁴, X⁵ and X⁶ independently represents hydrogen, —OH,

wherein, when K¹ represents the structure represented by formula (I-1-a)or formula (I-1-b), each of X¹ and X² independently represents

and

when K¹ represents the structure represented by formula (I-1-c), each ofX³, X⁴, X⁵ and X⁶ represents hydrogen or

The structure represented by formula (I-1) is also a rod-shapedstructure. This rod-shaped structure has a first axial direction and asecond axial direction. The above first axial direction is the longaxial direction of the rod-shaped structure, that is, the direction inwhich the functional group R¹ and the functional group K¹ are connected.The second axial direction is the short axial direction of therod-shaped structure, that is, a direction perpendicular to the firstaxial direction.

In the above formula (I-1), at least one of the functional groups X¹,X², X³, X⁴, X⁵, and X⁶ may include an anchoring group. The anchoringgroup may generate a bond or a hydrogen bond with a substrate (forexample, glass or ITO), and therefore, the additive molecules can beadsorbed (or fixed) on the substrate. For example, the anchoring groupmay include —OH,

In some embodiments, the anchoring group is one of X¹, X², X³, X⁴, X⁵,and X⁶ that is closest to the right end of the molecule represented byformula (I-1) such that the first axis is perpendicular to the topsurface of the substrate. As a result, the vertical alignment of theliquid-crystal molecules can be well achieved.

In some embodiments, each of the additive molecules has only oneanchoring group. Therefore, each of the additive molecules has the samealignment direction on the substrate. In other words, the first axialdirections of the different additive molecules are parallel to eachother. As a result, the liquid-crystal molecules can be aligned in auniform state, and defects (for example, local bright spots generated inthe dark state) are not easy to generate. In other embodiments, each ofthe additive molecules has two anchoring groups. Therefore, it ishelpful for the immobilization of the additive molecules on thesubstrate without being easy to detach. As a result, the occurrence ofdefects can also be reduced. In addition, in order to avoid the polarityof the additive molecules being too high to be dissolved in theliquid-crystal composition, the number of anchoring groups in oneadditive molecule is not greater than three.

In the above formula (I-1), the cyclic functional groups (i.e., A¹ andA²) may be an aliphatic ring or an aromatic ring. The cyclic functionalgroup contributes to the alignment of the liquid-crystal molecules. Morespecifically, the aromatic cyclic functional group may generate a π-πstacking so that the rod-shaped liquid-crystal molecules may be alignedin a specific direction. The aliphatic cyclic functional group can alignthe rod-shaped liquid-crystal molecules in a specific direction bysteric hindrance. In some embodiments, the first axial direction of theadditive molecules is perpendicular to the top surface of the substrate,and the long axis of the rod-shaped liquid-crystal molecules is parallelto the first axial direction of the additive molecules. Therefore, thelong axis of the rod-shaped liquid-crystal molecules can be madeperpendicular to the substrate by the additive molecules. In otherwords, the vertical alignment of the liquid-crystal molecules can beachieved.

Some negative ions (for example, fluoride ions) may remain in theliquid-crystal composition. These ions can cause residual current andreduce the voltage holding ratio during the operation of the display.More specifically, the higher concentration of the negative ions resultsin the lower the voltage holding ratio. Silicon atoms are moreelectron-poor than carbon atoms, and therefore, silicon atoms canattract (or capture) the negative ions in the liquid-crystalcomposition. As a result, the concentration of the negative ions in theliquid-crystal composition can be lowered, and the voltage holding ratioof the liquid-crystal display device can be increased. In other words,in the molecule represented by formula (I-1), the silicon atom has thefunction of increasing the voltage holding ratio. Furthermore, in orderto attract the negative ions, the silicon atom in the moleculerepresented by formula (I-1) is not directly bonded to the oxygen atom.In addition, because the silicon atom is bonded to the alkyl group, thesolubility of the molecule represented by formula (I-1) in theliquid-crystal composition can also be improved.

In some embodiments, in the above formula (I-1), at least one of thefunctional groups X¹, X², X³, X⁴, X⁵, and X⁶ may include a polymerizablegroup. The polymerizable group can make the additive molecules form theabove-mentioned network structure. As a result, the degree of verticalalignment of the liquid-crystal molecules is further improved, and thestability of the alignment ability is increased. The polymerizable groupmay include an acrylic group, a methacrylic group, or a derivativethereof. In some embodiments, at least one of the functional groups X¹,X², X³, X⁴, X⁵, and X⁶ is a polymerizable group having the followingstructure:

wherein Y¹ represents —OH, a C₁-C₈ alkyl group, or a C₂-C₈ alkenylgroup, and at least one hydrogen atom of the C₁-C₈ alkyl group or theC₂-C₈ alkenyl group is substituted by —OH; and Y² represents hydrogen,halogen, a C₁-C₈ alkyl group, or a C₂-C₈ alkenyl group, wherein theC₁-C₈ alkyl group or the C₂-C₈ alkenyl group is unsubstituted or atleast one hydrogen atom of the C₁-C₈ alkyl group or the C₂-C₈ alkenylgroup is substituted by a halogen atom.

Specific exemplary first additive molecules are shown in Table 1 below.Specific exemplary second additive molecules are shown in Table 2 below.Specific exemplary third additive molecules are shown in Table 3 below.

TABLE 1

Exp-A1

Exp-A2

Exp-A3

Exp-A4

Exp-A5

Exp-A6

Exp-A7

Exp-A8

Exp-A9

Exp-A10

Exp-A11

Exp-A12

Exp-A13

Exp-A14

Exp-A15

Exp-A16

TABLE 2

Exp-B1

Exp-B2

Exp-B3

Exp-B4

Exp-B5

Exp-B6

Exp-B7

Exp-B8

Exp-C1

Exp-C2

Exp-C3

Exp-C4

Exp-C5

Exp-C6

Referring to Table 1, in the first additive molecule, the rightmostcyclic functional group of the main chain of the molecule include a sidechain functional group at its opposite sides, respectively. Each ofthese side chain functional groups includes at least one cyclicfunctional group and at least one polymerizable group. Therefore, thefirst additive molecule can form the above-mentioned network structurewith adjacent additive molecules (for example, the first additivemolecule, the second additive molecule, and/or the third additivemolecule). Furthermore, in the formed network structure, the distancebetween adjacent additive molecules is fixed and uniform. As a result,the stability of the alignment ability of the liquid-crystal moleculescan be greatly improved.

Referring to Table 2, in the second additive molecule, the functionalgroup at the end of the molecular main chain includes a polymerizablegroup and an anchoring group. The second additive molecule can beadsorbed (or fixed) on the substrate in such a manner that the firstaxial direction is perpendicular to the top surface of the substrate,thereby obtaining good vertical alignment ability. Furthermore, aplurality of second additive molecules that are perpendicular to thesubstrate and arranged in parallel with each other can form theabove-mentioned network structure with adjacent additive molecules (forexample, the first additive molecule, the second additive molecule,and/or the third additive molecule). This network structure can furtherimprove the degree of vertical alignment of the liquid-crystal moleculesand improve the stability of the alignment ability.

Referring to Table 3, in the third additive molecule, the molecular sidechain includes at least one polymerizable group. The third additivemolecule may form the above-mentioned network structure with theadjacent additive molecule (for example, the first additive molecule,the second additive molecule, and/or the third additive molecule). As aresult, the stability of the alignment ability can be further improved.

In some embodiments, the additive includes one or more first additivemolecule. Therefore, this additive can have good stability of thealignment ability.

In some embodiments, the additive includes one or more first additivemolecule and one or more second additive molecule. In such embodiments,the second additive molecule (or the first additive molecule) having ananchoring group may be vertically fixed on the substrate, and may bebonded to adjacent first additive molecules or second additive moleculesto form the above-mentioned network structure. Therefore, this additivecan have excellent vertical alignment ability and excellent stability ofthe alignment ability. In such embodiments, when the amount of the firstadditive molecule is set to 1 part by weight, the amount of the secondadditive molecule is 0.01-60 parts by weight. In other embodiments, whenthe amount of the first additive molecule is set to 1 part by weight,the amount of the second additive molecule is 0.02-40 parts by weight.In still other embodiments, when the amount of the first additivemolecule is set to 1 part by weight, the amount of the second additivemolecule is 0.05-20 parts by weight.

In some embodiments, the additive includes one or more first additivemolecule and one or more third additive molecule. In such embodiments,the first additive molecule having an anchoring group may be verticallyfixed on the substrate, and may be bonded to adjacent first additivemolecules or third additive molecules to form the above-mentionednetwork structure. Therefore, this additive can have excellent verticalalignment ability and excellent stability of the alignment ability. Insuch embodiments, when the amount of the first additive molecule is setto 1 part by weight, the amount of the third additive molecule is0.01-80 parts by weight. In other embodiments, when the amount of thefirst additive molecule is set to 1 part by weight, the amount of thethird additive molecule is 0.05-70 parts by weight. In still otherembodiments, when the amount of the first additive molecule is set to 1part by weight, the amount of the third additive molecule is 0.07-60parts by weight.

In some embodiments, the additive includes one or more first additivemolecule, one or more second additive molecule, and one or more thirdadditive molecule. In such embodiments, the second additive molecule (orthe first additive molecule) having an anchoring group may be verticallyfixed on the substrate, and may be bonded to adjacent first additivemolecules, second additive molecules, or third additive molecules toform the above-mentioned network structure. Therefore, this additive canhave excellent vertical alignment ability and excellent stability of thealignment ability. In such embodiments, when the amount of the firstadditive molecule is set to 1 part by weight, the amount of the secondadditive molecule is 0.01-60 parts by weigh, and the amount of the thirdadditive molecule is 0.01-80 parts by weight. In other embodiments, whenthe amount of the first additive molecule is set to 1 part by weight,the amount of the second additive molecule is 0.03-45 parts by weigh,and the amount of the third additive molecule is 0.04-65 parts byweight. In still other embodiments, when the amount of the firstadditive molecule is set to 1 part by weight, the amount of the secondadditive molecule is 0.06-25 parts by weigh, and the amount of the thirdadditive molecule is 0.06-55 parts by weight.

In other embodiments, a liquid-crystal composition is provided. Theliquid-crystal composition includes a first component and a secondcomponent. The first component includes at least one additive asmentioned above, and the second component includes at least one compoundrepresented by formula (II):

wherein

each of R²¹ and R²² independently represents hydrogen, halogen, a C₁-C₁₅alkyl group, or a C₂-C₁₅ alkenyl group, wherein the C₁-C₁₅ alkyl groupor the C₂-C₁₅ alkenyl group is unsubstituted or at least one hydrogenatom of the C₁-C₁₅ alkyl group or the C₂-C₁₅ alkenyl group issubstituted by a halogen atom, and/or at least one —CH₂— of the C₁-C₁₅alkyl group or the C₂-C₁₅ alkenyl group is substituted by —O—, andwherein the —O— does not directly bond to another —O—;

each of B¹, B², and B³ independently represents a 1,4-phenylene group, a1,4-cyclohexylene group, a benzofuran-2,5-diyl group, a1,3-dioxane-2,5-diyl group, a tetrahydropyran-2,5-diyl group, a divalentdioxabicyclo[2.2.2]octylene group, a divalenttrioxabicyclo[2.2.2]octylene group, a tetrahydronaphthalene-2,6-diylgroup, or an indane-2,5-diyl group, wherein the 1,4-phenylene group, the1,4-cyclohexylene group, the 1,3-dioxane-2,5-diyl group, thebenzofuran-2,5-diyl group, the tetrahydronaphthalene-2,6-diyl group, theindane-2,5-diyl group, or the tetrahydropyran-2,5-diyl group isunsubstituted or at least one hydrogen atom of the 1,4-phenylene group,the 1,4-cyclohexylene group, the 1,3-dioxane-2,5-diyl group, thebenzofuran-2,5-diyl group, the tetrahydronaphthalene-2,6-diyl group, theindane-2,5-diyl group, or the tetrahydropyran-2,5-diyl group issubstituted by a halogen atom or a —CN group, and/or at least one —CH₂—of the 1,4-phenylene group, the 1,4-cyclohexylene group, the1,3-dioxane-2,5-diyl group, the benzofuran-2,5-diyl group, thetetrahydronaphthalene-2,6-diyl group, the indane-2,5-diyl group, or thetetrahydropyran-2,5-diyl group is substituted by —O—, —N— or —S—, andwherein the —O—, —N—, and —S— do not directly bond to one another;

each of Z²¹ and Z²² independently represents a single bond, a C₁-C₄alkylene group, a C₂-C₄ alkenylene group, or a C₂-C₄ alkynylene group,wherein the C₁-C₄ alkylene group, the C₂-C₄ alkenylene group, or theC₂-C₄ alkynylene group is unsubstituted or at least one hydrogen atom ofthe C₁-C₄ alkylene group, the C₂-C₄ alkenylene group, or the C₂-C₄alkynylene group is substituted by a halogen atom or a —CN group, and/orat least one —CH₂— of the C₁-C₄ alkylene group, the C₂-C₄ alkenylenegroup, or the C₂-C₄ alkynylene group is substituted by —O— or —S—, andwherein the —O— does not directly bond to —O— or —S—, and —S— does notdirectly bond to —S—; and n²¹ represents 0, 1, or 2, and when n²¹represents 2, the two B¹ groups are identical to each other or differentfrom each other.

In accordance with some embodiments, the above-mentioned secondcomponent includes at least one compound represented by formula (II-1)or formula (II-2):

wherein

the definitions of R²¹, R²², B¹, B², Z²², and n²¹ are respectively thesame as the definitions of R²¹, R²², B¹, B², Z²², and n²¹ defined in theprevious paragraphs.

Because the cyclic group of the compound represented by formula (II-1)has no fluorine atom, the viscosity of the liquid-crystal compositioncan be lowered, and the response speed of the liquid-crystal moleculescan be improved when a voltage is applied. The compound represented byformula (II-2) includes at least one phenylene group, and two hydrogenatoms on the same side of this phenylene group are substituted byfluorine atoms. The compound of formula (II-2) can be used to adjust thedielectric anisotropy (A e) of the liquid-crystal composition.

In accordance with some embodiments, the above-mentioned liquid-crystalcomposition further includes a third component, and the third componentincludes at least one compound represented by formula (III), formula(IV), or formula (V):

wherein

each of K²¹, K²², K²³, and K²⁴ independently represents hydrogen or amethyl group;

each of Z²³ and Z²⁴ independently represents a single bond, a C₁-C₁₅linear alkylene group, a C₃-C₁₅ branched alkylene group, a C₂-C₁₅ linearalkenylene group, or a C₃-C₁₅ branched alkenylene group, wherein theC₁-C₁₅ linear alkylene group, the C₃-C₁₅ branched alkylene group, theC₂-C₁₅ linear alkenylene group, or the C₃-C₁₅ branched alkenylene groupis unsubstituted or at least one hydrogen atom of the C₁-C₁₅ linearalkylene group, the C₃-C₁₅ branched alkylene group, the C₂-C₁₅ linearalkenylene group, or the C₃-C₁₅ branched alkenylene group is substitutedby a halogen atom, and/or at least one —CH₂— of the C₁-C₁₅ linearalkylene group, the C₃-C₁₅ branched alkylene group, the C₂-C₁₅ linearalkenylene group, or the C₃-C₁₅ branched alkenylene group is substitutedby —O—, —CO—, —COO—, or —OCO—, and wherein the —O—, —CO—, —COO—, and—OCO— do not directly bond to one another;

each of Z²⁵, Z²⁶, Z²⁷, and Z²⁸ independently represents a single bond,—C≡C—, a C₁-C₁₅ linear alkylene group, a C₃-C₁₅ branched alkylene group,a C₂-C₁₅ linear alkenylene group, or a C₃-C₁₅ branched alkenylene group,wherein the C₁-C₁₅ linear alkylene group, the C₃-C₁₅ branched alkylenegroup, the C₂-C₁₅ linear alkenylene group, or the C₃-C₁₅ branchedalkenylene group is unsubstituted or at least one hydrogen atom of theC₁-C₁₅ linear alkylene group, the C₃-C₁₅ branched alkylene group, theC₂-C₁₅ linear alkenylene group, or the C₃-C₁₅ branched alkenylene groupis substituted by a halogen atom, and/or at least one —CH₂— of theC₁-C₁₅ linear alkylene group, the C₃-C₁₅ branched alkylene group, theC₂-C₁₅ linear alkenylene group, or the C₃-C₁₅ branched alkenylene groupis substituted by —SiR^(e) ₂—, —S—, —O—, —CO—, —COO—, —OCO—,—CO—NR^(e)—, or —NR^(e)—CO—, and the —SiR^(e) ₂—, —S—, —O—, —CO—, —COO—,—OCO—, —CO—NR^(e)—, and —NR^(e)—CO— do not directly bond to one another,wherein R^(e) represents hydrogen, a C₁-C₄ linear alkyl group, or aC₃-C₄ branched alkyl group, and the two R^(e) groups bonded to the sameSi atom are identical to each other or different from each other;

each of B⁴, B⁵, B⁶ and B⁷ independently represents a 1,4-phenylenegroup, a 1,4-cyclohexylene group, a benzofuran-2,5-diyl group, a1,3-dioxane-2,5-diyl group, a tetrahydropyran-2,5-diyl group, a divalentdioxabicyclo[2.2.2]octylene group, a divalenttrioxabicyclo[2.2.2]octylene group, a tetrahydronaphthalene-2,6-diylgroup, or an indane-2,5-diyl group, wherein the 1,4-phenylene group, the1,4-cyclohexylene group, the benzofuran-2,5-diyl group, the1,3-dioxane-2,5-diyl group, the tetrahydropyran-2,5-diyl group, thedivalent dioxabicyclo[2.2.2]octylene group, the divalenttrioxabicyclo[2.2.2]octylene group, the tetrahydronaphthalene-2,6-diylgroup, or the indane-2,5-diyl group is unsubstituted or is substitutedby at least one substituent, wherein the at least one substituent isselected from fluorine, chlorine, a —CN group, a C₁-C₁₂ linear alkylgroup, a C₃-C₁₂ branched alkyl group, a C₂-C₁₂ linear alkenyl group, aC₂-C₁₂ linear alkynyl group, a C₄-C₁₂ branched alkenyl group, or aC₄-C₁₂ branched alkynyl group, wherein the C₁-C₁₂ linear alkyl group,the C₃-C₁₂ branched alkyl group, the C₂-C₁₂ linear alkenyl group, theC₂-C₁₂ linear alkynyl group, the C₄-C₁₂ branched alkenyl group, or theC₄-C₁₂ branched alkynyl group is unsubstituted or at least one hydrogenatom of the C₁-C₁₂ linear alkyl group, the C₃-C₁₂ branched alkyl group,the C₂-C₁₂ linear alkenyl group, the C₂-C₁₂ linear alkynyl group, theC₄-C₁₂ branched alkenyl group, or the C₄-C₁₂ branched alkynyl group issubstituted by a halogen atom, and/or at least one —CH₂— of the C₁-C₁₂linear alkyl group, the C₃-C₁₂ branched alkyl group, the C₂-C₁₂ linearalkenyl group, the C₂-C₁₂ linear alkynyl group, the C₄-C₁₂ branchedalkenyl group, or the C₄-C₁₂ branched alkynyl group is substituted by—O—, —CO—, —COO—, or —OCO—, and the —O—, —CO—, —COO—, and —OCO— do notdirectly bond to one another;

M¹ represents a single bond, —CH₂O—, —OCH₂—, —CH₂CH₂—, —CH═CH—, —C≡C—,—CH₂—, —C(CH₃)₂—, —C(CF₃)₂—, —SiH₂—, —Si(CH₃)₂—, or —Si(CF₃)₂—;

each of R²³ and R²⁴ independently represents a C₁-C₃₀ linear alkyl groupor a C₃-C₃₀ branched alkyl group, wherein the C₁-C₃₀ linear alkyl groupor the C₃-C₃₀ branched alkyl group is unsubstituted or at least onehydrogen atom of the C₁-C₃₀ linear alkyl group or the C₃-C₃₀ branchedalkyl group is substituted by a halogen atom, and/or at least one —CH₂—of the C₁-C₃₀ linear alkyl group or the C₃-C₃₀ branched alkyl group issubstituted by —Si—, —O—, —CO—, —COO—, or —OCO—, and the —Si—, —O—,—CO—, —COO—, and —OCO— do not directly bond to one another; and

each of n²² and n²³ independently represents an integer of 0 to 3, andwhen n²² is 2 or more, the two or more B⁴ groups are identical to eachother or different from each other, and the two or more M¹ groups areidentical to each other or different from each other; and when n²³ is 2or more, the two or more B⁶ groups are identical to each other ordifferent from each other, and the two or more Z²⁷ groups are identicalto each other or different from each other.

The compound of the third component includes at least one polymerizablegroup, and the polymerizable group may include an acrylic group, amethacrylic group, or a derivative thereof. More specifically, each ofthe compounds represented by formula (IV) and formula (V) has apolymerizable group at one end of the molecule. Each of the compoundsrepresented by formula (III) has a polymerizable group at both ends ofthe molecule. By irradiation or heating, the polymerizable group of thethird component may undergo the polymerization reaction with anotherpolymerizable group of the above-mentioned additive moleculesrepresented by formula (I). In this way, it is helpful to form theabove-mentioned network, and the degree of vertical alignment of theliquid-crystal molecules can be further improved.

If the content of the first component is too low, the degree of verticalalignment and the voltage holding ratio of the liquid-crystalcomposition may not be effectively improved. On the contrary, if thecontent of the first component is too high, the first component may notdissolve well in the liquid-crystal composition, and it may precipitate.Such a liquid-crystal composition cannot be used. Furthermore, when thefirst component exceeds the specific content, even if the firstcomponent is further increased, the degree of vertical alignment of theliquid-crystal composition cannot be further improved. Furthermore, thefirst component has the group (for example, an anchoring group) having arelatively high polarity. Therefore, if the content of the firstcomponent is too high, the voltage holding ratio of the liquid-crystalcomposition may be lowered. As described above, in order to balance thedegree of vertical alignment and the voltage holding ratio of theliquid-crystal composition, the content of the first component may becontrolled within an appropriate range.

In some embodiments, the liquid-crystal composition includes a firstcomponent and a second component. In such embodiments, when the totalweight of the second component is 100 parts by weight, the firstcomponent is 0.01-10 parts by weight. In other embodiments, when thetotal weight of the second component is 100 parts by weight, the firstcomponent is 0.05-6 parts by weight. In still other embodiments, whenthe total weight of the second component is 100 parts by weight, thefirst component is 0.1-4 parts by weight.

In some embodiments, the liquid-crystal composition includes a firstcomponent, a second component, and a third component. In suchembodiments, when the total weight of the second component is 100 partsby weight, the first component is 0.01-10 parts by weight, and the thirdcomponent is 0.01-10 parts by weight. In other embodiments, when thetotal weight of the second component is 100 parts by weight, the firstcomponent is 0.04-5 parts by weight, and the third component is 0.04-4parts by weight. In still other embodiments, when the total weight ofthe second component is 100 parts by weight, the first component is0.07-3.5 parts by weight, and the third component is 0.07-2.5 parts byweight.

For those skilled in the art, it should be understood that theliquid-crystal composition may further include other components otherthan the above-mentioned first component, second component, and thirdcomponent. For example, other conventional liquid-crystal compounds orother additives in appropriate amounts. In some embodiments, theabove-mentioned other additives may include, for example, chiraldopants, UV stabilizers, antioxidants, free radical scavengers,nanoparticles, and so on.

In the present disclosure, a liquid-crystal display device using theabove-mentioned liquid-crystal composition is also provided. The FIGUREis a cross-sectional view showing a liquid-crystal display device 100 inaccordance with some embodiments of the present disclosure.

Referring to the FIGURE, the liquid-crystal display device 100 includesa first substrate 110 and a second substrate 120 disposed opposite tothe first substrate 110. The liquid-crystal display device 100 alsoincludes a liquid-crystal layer 130 disposed between the first substrate110 and the second substrate 120. The first substrate 110 and the secondsubstrate 120 are respectively a conventional thin film transistorsubstrate and a conventional color filter substrate. In order tosimplify the description, the materials, structures, and manufacturingmethods of the first substrate 110 and the second substrate 120 will notbe described in detail herein.

The liquid-crystal layer 130 of the liquid-crystal display device 100 ofthe present disclosure uses the above-mentioned liquid-crystalcomposition, and the liquid-crystal composition includes the additiverepresented by formula (I) and/or formula (I-1) (i.e., the additiveincludes the first additive molecule, the second additive molecule,and/or the third additive molecule). As described above, such anadditive can greatly improve the degree of vertical alignment, thevoltage holding ratio, and the stability of the alignment ability of theliquid-crystal composition. By adding the above-mentioned additive tothe liquid-crystal composition, the liquid-crystal molecules can bevertically aligned well without using a conventional alignment film. Onthe other hand, the liquid-crystal display device 100 using theabove-mentioned additive has the advantages of high voltage holdingratio and good durability. The liquid-crystal composition of the presentdisclosure can be applied to all kinds of liquid-crystal displaydevices.

In order to further simplify and clarify the foregoing contents andother objects, characteristics, and merits of the present disclosure, afew examples are given to explain the additives and the liquid-crystalcompositions of the present disclosure. The chemical structures andcontents corresponding to the compounds of the second component and thethird component used in the liquid-crystal compositions of the Examplesare shown in Table 4 below. The additive molecules of the ReferenceExamples are shown in Table 5 below.

TABLE 4 Content Chemical structure (wt %) formula (II) formula (II-1)

10

5

12

14 formula (II-2)

10

19

15

15 formula (III)

0.3

TABLE 5 No. Chemical structure Ref

The synthesis methods of the additive molecules of the Examples and theReference Examples are described as follows.

Preparation Example 1 Preparing the Additive Molecule Exp-A1

The synthesis flow of the additive molecule Exp-A1 is shown above.Compound 1 (30 g, 91.3 mmol), diisopropylamine (1.3 g, 12.8 mmol),N-bromosuccinimide (NBS, 33.3 g, 187.2 mmol), and dichloromethane (400mL) were placed in a 1000 mL reaction flask and stirred to dissolve. Thereaction was carried out at room temperature (20-30° C.) for 6 hours.After the reaction was completed, water was added. Then, an extractionwas performed by using dichloromethane and water, and the organic phasewas collected. The solvent of the collected organic phase was removed byusing a rotary concentrator. Then, column chromatography was performedto obtain Compound 2.

Sodium hydride (4.2 g, 173 mmol), dimethylformamide (DMF, 200 mL), andCompound 2 (24.0 g, 49.4 mmol) were placed in a 500 mL double-neckedround bottom flask and stirred for 30 minutes. Then, iodoethane (23.1 g,148.1 mmol) was added at 0° C., and the reaction was carried out at 100°C. for 8 hours. After the reaction was completed, water was added. Then,an extraction was performed by using ethyl acetate and water, and theorganic phase was collected. The solvent of the collected organic phasewas removed by using a rotary concentrator. Then, column chromatographywas performed to obtain Compound 3.

Compound 3 (8.0 g, 15.6 mmol), 4-hydroxyphenylboronic acid (5.4 g, 38.9mmol), tetrahydrofuran (THF, 140 mL), water (30 mL), and potassiumcarbonate (17.2 g, 124.5 mmol) were placed in a 500 mL reaction flaskand stirred to dissolve. Deoxygenation was performed by introducingnitrogen for 30 minutes. Then, tetrakis(triphenylphosphine)palladium(0)(1.8 g, 1.6 mmol) was added, and the mixture was heated to reflux for 24hours to carry out the reaction. After the reaction was completed, anextraction was performed by using ethyl acetate and water, and theorganic phase was collected. The solvent of the collected organic phasewas removed by using a rotary concentrator. Then, column chromatographywas performed to obtain Compound 4.

Compound 4 (3.0 g, 5.6 mmol), Compound 5 (4.7 g, 25.0 mmol),4-dimethylaminopyridine (DMAP, 0.68 g, 5.6 mmol), and tetrahydrofuran(40 mL) were placed in a 100 mL reaction flask and stirred to dissolve.Then, N,N′-dicyclohexylcarbodiimide (DCC, 3.0 g, 14.4 mmol) was added at0° C., and the reaction was carried out at room temperature (20-30° C.)for 24 hours. After the reaction was completed, water was added. Then,an extraction was performed by using ethyl acetate and water, and theorganic phase was collected. The solvent of the collected organic phasewas removed by using a rotary concentrator. Then, column chromatographywas performed to obtain Compound 6.

Compound 6 (1.8 g, 2.1 mmol), pyridinium p-toluenesulfonate (1.0 g, 4.1mmol), methanol (40 mL), and tetrahydrofuran (40 mL) were placed in a250 mL reaction flask and stirred to dissolve. The reaction was carriedout at 50° C. for 10 hours. After the reaction was completed, water wasadded. Then, an extraction was performed by using ethyl acetate andwater, and the organic phase was collected. The solvent of the collectedorganic phase was removed by using a rotary concentrator. Then, columnchromatography was performed to obtain the additive molecule Exp-A1(white solid).

The additive molecule Exp-A1 was analyzed by nuclear magnetic resonancespectroscopy, and the obtained spectral information was as follows: ¹HNMR (CDCl₃, 400 MHz): δ 0.82-1.38 (m, 23H), 1.72-2.06 (m, 11H),2.45-2.55 (m, 2H), 3.30 (q, J=7.2 Hz, 2H), 4.50 (s, 4H), 6.09 (s, 2H),6.57 (s, 2H), 7.20-7.22 (m, 6H), 7.69 (d, J=8.8 Hz, 4H).

Preparation Example 2 Preparing the Additive Molecule Exp-A2

The synthesis flow of the additive molecule Exp-A2 is shown above.Compound 4 (3.0 g, 5.6 mmol), methacrylic acid (2.6 g, 30.6 mmol),4-dimethylaminopyridine (0.68 g, 5.6 mmol), and tetrahydrofuran (100 mL)were placed in a 250 mL reaction flask and stirred to dissolve. Then,N,N′-dicyclohexylcarbodiimide (2.7 g, 13.3 mmol) was added at 0° C., andthe reaction was carried out at room temperature (20-30° C.) for 24hours. After the reaction was completed, water was added. Then, anextraction was performed by using ethyl acetate and water, and theorganic phase was collected. The solvent of the collected organic phasewas removed by using a rotary concentrator. Then, column chromatographywas performed to obtain the additive molecule Exp-A2 (white solid).

The additive molecule Exp-A2 was analyzed by nuclear magnetic resonancespectroscopy, and the obtained spectral information was as follows: ¹HNMR (CDCl₃, 400 MHz): δ 0.82-1.50 (m, 25H), 1.72-1.99 (m, 8H), 2.11 (s,6H), 2.48-2.54 (m, 1H), 3.30 (q, J=6.8 Hz, 2H), 5.79 (s, 2H), 6.40 (s,2H), 7.19-7.21 (m, 6H), 7.67 (d, J=8.8 Hz, 4H).

Preparation Example 3 Preparing the Additive Molecule Exp-A3

The synthesis flow of the additive molecule Exp-A3 is shown above.Compound 4 (1.89 g, 3.5 mmol) and dimethylformamide (50 mL) were placedin a 250 mL reaction flask and dissolved. Then, sodium hydride (0.4 g,16 mmol) was added under an ice bath, and the mixture was stirred atroom temperature for 30 minutes. Next,(3-bromopropoxy)-tert-butyldimethylsilane (4.0 g, 16 mmol) was added,and the reaction was carried out at room temperature for 2 hours. Afterthe reaction was completed, an extraction was performed by using ethylacetate and water, and the mixture was dried by using magnesium sulfate.The organic phase was collected. The solvent of the collected organicphase was removed by using a rotary concentrator. Then, columnchromatography was performed to obtain Compound 7 (clear oil).

Compound 7 (2.79 g, 3.2 mmol) and tetrahydrofuran (50 mL) were placed ina 250 mL reaction flask and dissolved and cooled to 0° C. Then,tetrabutylammonium fluoride solution (solvent: tetrahydrofuran; 1 M, 9.6ml, 9.6 mmol) was slowly added, and the mixture was warmed to roomtemperature and stirred for 2 hours. After the reaction was completed,an extraction was performed by using ethyl acetate and water, and themixture was dried by using magnesium sulfate. The organic phase wascollected. The solvent of the collected organic phase was removed byusing a rotary concentrator. Then, column chromatography was performedto obtain Compound 8 (white solid).

Compound 8 (1.97 g, 3 mmol), methacrylic acid (0.77 g, 9 mmol),4-dimethylaminopyridine (0.21 g, 1.8 mmol), and tetrahydrofuran (50 mL)were placed in a 250 mL reaction flask and stirred to dissolve. Then,the temperature of the reaction flask was cooled to 0° C. Next,N,N′-dicyclohexylcarbodiimide (1.9 g, 9 mmol) was dissolved intetrahydrofuran (20 mL) to form a solution, and the solution was slowlyadded dropwise to the reaction flask. The mixture was stirred at 0° C.for 30 minutes, and then, was warmed to room temperature and stirred for8 hours. After the reaction was completed, an extraction was performedby using ethyl acetate and water, and the mixture was dried by usingmagnesium sulfate. The organic phase was collected. The solvent of thecollected organic phase was removed by using a rotary concentrator.Then, column chromatography was performed to obtain the additivemolecule Exp-A3 (white solid).

The additive molecule Exp-A3 was analyzed by nuclear magnetic resonancespectroscopy, and the obtained spectral information was as follows: ¹HNMR (CDCl₃, 400 MHz): δ 0.82-1.48 (m, 32H), 1.75-1.84 (m, 8H), 1.96 (s,6H), 2.21 (m, 4H), 2.47 (m, 1H), 3.27 (q, J=6.8 Hz, 2H), 4.12 (t, J=6.4Hz, 4H), 4.38 (t, J=6.4 Hz, 4H), 5.58 (t, J=1.2 Hz, 2H), 6.13 (q, J=0.8Hz, 2H), 6.94 (d, J=9.2 Hz, 4H), 7.11 (s, 2H), 7.56 (d, J=8.8 Hz, 4H).

Preparation Example 4 Preparing the Additive Molecule Exp-A4

The synthesis flow of the additive molecule Exp-A4 is shown above.Compound 2 (17.8 g, 37 mmol) and dimethylformamide (200 mL) were placedin a 500 mL reaction flask and dissolved. Then, sodium hydride (2.7 g,111 mmol) was added under an ice bath, and the mixture was stirred atroom temperature for 30 minutes. Next, 2-(3-bromopropoxy)tetrahydropyran (24.8 g, 111 mmol) was added, and the reaction wascarried out at room temperature for 4 hours. After the reaction wascompleted, an extraction was performed by using ethyl acetate and water,and the mixture was dried by using magnesium sulfate. The organic phasewas collected. The solvent of the collected organic phase was removed byusing a rotary concentrator. Then, column chromatography was performedto obtain Compound 9 (clear oil).

Compound 9 (16.3 g, 26 mmol), 4-hydroxyphenylboronic acid (9.0 g, 65mmol), potassium carbonate (18.0 g, 130 mmol), tetrahydrofuran (200 mL),and water (60 mL) were placed in a 500 mL reaction flask and stirred todissolve. Deoxygenation was performed by introducing nitrogen, and themixture was stirred vigorously for 1 hour. Then,tetrakis(triphenylphosphine) palladium(0) (0.751 g, 0.65 mmol) wasadded, and the mixture was heated to reflux at 70° C. for 8 hours tocarry out the reaction. After the reaction was completed, an extractionwas performed by using ethyl acetate and water, and the mixture wasdried by using magnesium sulfate. The organic phase was collected. Thesolvent of the collected organic phase was removed by using a rotaryconcentrator. Then, column chromatography was performed to obtainCompound 10 (pale yellow solid).

Compound 10 (8.3 g, 10.4 mmol), methacrylic acid (2.24 g, 26 mmol),4-dimethylaminopyridine (0.79 g, 6.5 mmol), and tetrahydrofuran (120 mL)were placed in a 250 mL reaction flask and stirred to dissolve. Then,the temperature of the reaction flask was cooled to 0° C. Next,N,N′-dicyclohexylcarbodiimide (5.4 g, 26 mmol) was dissolved intetrahydrofuran (30 mL) to form a solution, and the solution was slowlyadded dropwise to the reaction flask. The mixture was stirred at 0° C.for 30 minutes, and then, was warmed to room temperature and stirred for3 hours. After the reaction was completed, an extraction was performedby using ethyl acetate and water, and the mixture was dried by usingmagnesium sulfate. The organic phase was collected. The solvent of thecollected organic phase was removed by using a rotary concentrator.Then, column chromatography was performed to obtain Compound 11 (whitesolid).

Compound 11 (6.2 g, 7.8 mmol), pyridinium p-toluenesulfonate (0.49 g,3.9 mmol), tetrahydrofuran (60 mL), and methanol (60 mL) were placed ina 250 mL reaction flask and stirred to dissolve. The mixture was stirredat 50° C. for 3 hours. After the reaction was completed, the insolublematter was separated by filtration. Then, an extraction was performed byusing ethyl acetate and water, and the mixture was dried by usingmagnesium sulfate. The organic phase was collected. The solvent of thecollected organic phase was removed by using a rotary concentrator.Then, column chromatography was performed to obtain the additivemolecule Exp-A4 (white solid).

The additive molecule Exp-A4 was analyzed by nuclear magnetic resonancespectroscopy, and the obtained spectral information was as follows: ¹HNMR (CDCl₃, 400 MHz): δ 0.89-1.50 (m, 29H), 1.72-2.0 (m, 7H), 2.09 (s,6H), 2.50 (m, 1H), 3.28 (t, J=5.2 Hz, 2H), 3.34 (t, J=0.8 Hz, 2H), 5.79(s, 2H), 6.39 (s, 2H), 7.17 (s, 2H), 7.19 (d, J=2 Hz, 4H), 7.63 (d,J=8.8 Hz, 4H).

Preparation Example 5 Preparing the Additive Molecule Exp-A5

The synthesis flow of the additive molecule Exp-A5 is shown above.Compound 2 (15.4 g, 32 mmol), 2,2,5-trimethyl-[1,3]dioxane-5-carboxylicacid (8.4 g, 48 mmol), 4-dimethylaminopyridine (1.17 g, 9.6 mmol), andtetrahydrofuran (200 mL) were placed in a 500 mL reaction flask andstirred to dissolve. Then, the temperature of the reaction flask wascooled to 0° C. Next, N,N′-dicyclohexylcarbodiimide (9.9 g, 48 mmol) wasdissolved in tetrahydrofuran (50 mL) to form a solution, and thesolution was slowly added dropwise to the reaction flask. The mixturewas stirred at 0° C. for 30 minutes, and then, warmed to roomtemperature and stirred for 3 hours. After the reaction was completed,an extraction was performed by using ethyl acetate and water, and themixture was dried by using magnesium sulfate. The organic phase wascollected. The solvent of the collected organic phase was removed byusing a rotary concentrator. Then, column chromatography was performedto obtain Compound 12 (white solid).

Compound 12 (16.7 g, 26 mmol), 4-hydroxyphenylboronic acid (9.0 g, 65mmol), potassium carbonate (18.0 g, 130 mmol), tetrahydrofuran (200 mL),and water (60 mL) were placed in a 500 mL reaction flask and stirred todissolve. Deoxygenation was performed by introducing nitrogen, and themixture was stirred vigorously for 1 hour. Then,tetrakis(triphenylphosphine) palladium(0) (0.751 g, 0.65 mmol) wasadded, and the mixture was heated to reflux at 70° C. for 8 hours tocarry out the reaction. After the reaction was completed, an extractionwas performed by using ethyl acetate and water, and the mixture wasdried by using magnesium sulfate. The organic phase was collected. Thesolvent of the collected organic phase was removed by using a rotaryconcentrator. Then, column chromatography was performed to obtainCompound 13 (pale yellow solid).

Compound 13 (6.9 g, 10.4 mmol), methacrylic acid (2.24 g, 26 mmol),4-dimethylaminopyridine (0.79 g, 6.5 mmol), and tetrahydrofuran (120 mL)were placed in a 250 mL reaction flask and stirred to dissolve. Then,the temperature of the reaction flask was cooled to 0° C. Next,N,N′-dicyclohexylcarbodiimide (5.4 g, 26 mmol) was dissolved intetrahydrofuran (30 mL) to form a solution, and the solution was slowlyadded dropwise to the reaction flask. The mixture was stirred at 0° C.for 30 minutes, and then, was warmed to room temperature and stirred for3 hours. After the reaction was completed, an extraction was performedby using ethyl acetate and water, and the mixture was dried by usingmagnesium sulfate. The organic phase was collected. The solvent of thecollected organic phase was removed by using a rotary concentrator.Then, column chromatography was performed to obtain Compound 14 (whitesolid).

Compound 14 (4.1 g, 5.1 mmol) was placed in a 250 mL reaction flask anddissolved in tetrahydrofuran (120 mL). Then, hydrochloric acid (12 M, 2mL) was slowly added dropwise to the reaction flask, and the mixture wasstirred at room temperature for 2 hours. After the reaction wascompleted, the mixture was cooled to 0° C., and water was added to carryout the neutralization reaction. Then, an extraction was performed byusing ethyl acetate and water, and the mixture was dried by usingmagnesium sulfate. The organic phase was collected. The solvent of thecollected organic phase was removed by using a rotary concentrator.Then, column chromatography was performed to obtain the additivemolecule Exp-A5 (white solid).

The additive molecule Exp-A5 was analyzed by nuclear magnetic resonancespectroscopy, and the obtained spectral information was as follows: ¹HNMR (CDCl₃, 400 MHz): δ 0.89-1.50 (m, 29H), 1.72-2.0 (m, 9H), 2.09 (s,6H), 2.50 (m, 1H), 3.28 (t, J=5.2 Hz, 2H), 3.34 (t, J=0.8 Hz, 2H), 5.79(s, 2H), 6.39 (s, 2H), 7.17 (s, 2H), 7.19 (d, J=2 Hz, 4H), 7.63 (d,J=8.8 Hz, 4H).

Preparation Example 6 Preparing the Additive Molecule Exp-A6

The synthesis flow of the additive molecule Exp-A6 is shown above.Compound 13 (5.3 g, 8 mmol) and dimethylformamide (100 mL) were placedin a 250 mL reaction flask and dissolved. Then, sodium hydride (0.8 g,32 mmol) was added under an ice bath, and the mixture was stirred atroom temperature for 30 minutes. Next,(3-bromopropoxy)-tert-butyldimethylsilane (8.1 g, 32 mmol) was added,and the reaction was carried out at room temperature for 4 hours. Afterthe reaction was completed, an extraction was performed by using ethylacetate and water, and the mixture was dried by using magnesium sulfate.The organic phase was collected. The solvent of the collected organicphase was removed by using a rotary concentrator. Then, columnchromatography was performed to obtain Compound 15 (clear oil).

Compound 15 (5.3 g, 5 mmol) and tetrahydrofuran (100 mL) were placed ina 250 mL reaction flask and dissolved and cooled to 0° C. Then,tetrabutylammonium fluoride solution (1 M, 17.5 ml, 17.5 mmol) wasslowly added, and the mixture was warmed to room temperature and stirredfor 2 hours. After the reaction was completed, an extraction wasperformed by using ethyl acetate and water, and the mixture was dried byusing magnesium sulfate. The organic phase was collected. The solvent ofthe collected organic phase was removed by using a rotary concentrator.Then, column chromatography was performed to obtain Compound 16 (whitesolid).

Compound 16 (2.7 g, 3 mmol), methacrylic acid (1.24 g, 12 mmol),4-dimethylaminopyridine (0.29 g, 2.4 mmol), and tetrahydrofuran (100 mL)were placed in a 250 mL reaction flask and stirred to dissolve. Then,the temperature of the reaction flask was cooled to 0° C. Next,N,N′-dicyclohexylcarbodiimide (2.5 g, 12 mmol) was dissolved intetrahydrofuran (30 mL) to form a solution, and the solution was slowlyadded dropwise to the reaction flask. The mixture was stirred at 0° C.for 30 minutes, and then, was warmed to room temperature and stirred for3 hours. After the reaction was completed, an extraction was performedby using ethyl acetate and water, and the mixture was dried by usingmagnesium sulfate. The organic phase was collected. The solvent of thecollected organic phase was removed by using a rotary concentrator.Then, column chromatography was performed to obtain Compound 17 (whitesolid).

Compound 17 (0.46 g, 0.5 mmol) was placed in a 250 mL reaction flask anddissolved in tetrahydrofuran (50 mL). Then, hydrochloric acid (12 M, 0.5mL) was slowly added dropwise to the reaction flask, and the mixture wasstirred at room temperature for 3 hours. After the reaction wascompleted, the mixture was cooled to 0° C., and water was added to carryout the neutralization reaction. Then, an extraction was performed byusing ethyl acetate and water, and the mixture was dried by usingmagnesium sulfate. The organic phase was collected. The solvent of thecollected organic phase was removed by using a rotary concentrator.Then, column chromatography was performed to obtain the additivemolecule Exp-A6 (white solid).

The additive molecule Exp-A6 was analyzed by nuclear magnetic resonancespectroscopy, and the obtained spectral information was as follows: ¹HNMR (CDCl₃, 400 MHz): δ 0.77-1.44 (m, 32H), 1.71-1.84 (m, 8H), 1.96 (s,6H), 2.05 (s, 1H), 2.18 (t, J=6 Hz, 2H), 3.41 (dd, J=2.8 Hz, 4H), 4.10(t, J=2 Hz, 4H), 4.36 (t, J=2.4 Hz, 2H), 5.58 (t, J=1.6 Hz 2H), 6.12 (s,2H), 6.93 (d, J=8.8 Hz, 4H), 7.14 (s, 2H), 7.31 (d, J=8.8 Hz, 4H).

Preparation Example 7 Preparing the Additive Molecule Exp-B1

The synthesis flow of the additive molecule Exp-B1 is shown above.Compound 18 (24.7 g, 63.2 mmol) and anhydrous tetrahydrofuran (400 mL)were placed in a 1000 mL reaction flask and stirred to dissolve. Then,n-butyllithium (2.5 M, solvent: tetrahydrofuran; 26.5 mL, 66.2 mmol) wasslowly added dropwise to the reaction flask at −78° C., and the reactionwas carried out for 1 hour. Next, trichloro(methyl)silane (9.0 g, 60.2mmol) was added to the reaction flask at −78° C., and the reaction wascarried out at room temperature (20-30° C.) for 3 hours. Then,allylmagnesium chloride (concentration: 2.0M, solvent: tetrahydrofuran;63.2 mL, 126.4 mmol) was added, and the mixture was heated (100° C.) toreflux for 8 hours to carry out the reaction. After the reaction wascompleted, water was added. Then, an extraction was performed by usingethyl acetate and water, and the organic phase was collected. Thesolvent of the collected organic phase was removed by using a rotaryconcentrator. Then, column chromatography was performed to obtainCompound 19.

Compound 19 (17.0 g, 38.9 mmol) and tetrahydrofuran (550 mL) were placedin a 1000 mL reaction flask and stirred to dissolve. Then,borane-dimethyl sulfide complex (concentration: 2.0M, solvent:tetrahydrofuran; 42.8 mL, 85.6 mmol) was added to the reaction flask at0° C., and the reaction was carried out for 3 hours. Then, sodiumhydroxide (4.2 g, 105.1 mmol) was dissolved in 34 mL of pure water at 0°C. and stirred for 0.5 hour. Then, hydrogen peroxide (30%, 55 mL) wasadded to the reaction flask at 0° C., and the reaction was carried outat room temperature (20-30° C.) for 5 hours. After the reaction wascompleted, saturated potassium carbonate aqueous solution was added.Then, an extraction was performed by using ethyl acetate and water, andthe organic phase was collected. The solvent of the collected organicphase was removed by using a rotary concentrator. Then, columnchromatography was performed to obtain Compound 20.

Compound 20 (6.0 g, 12.7 mmol), acrylic acid (4.6 g, 63.5 mmol),4-dimethylaminopyridine (1.5 g, 12.7 mmol), and tetrahydrofuran (120 mL)were placed in a 500 mL reaction flask and stirred to dissolve. Then,N,N′-dicyclohexylcarbodiimide (6.3 g, 30.5 mmol) was added to thereaction flask at 0° C., and the reaction was carried out at roomtemperature (20-30° C.) for 24 hours. After the reaction was completed,an extraction was performed by using ethyl acetate and water, and theorganic phase was collected. The solvent of the collected organic phasewas removed by using a rotary concentrator. Then, column chromatographywas performed to obtain Compound 21.

Compound 21 (3.0 g, 5.2 mmol), paraformaldehyde (1.4 g, 46.5 mmol),1,4-diazabicyclo[2.2.2]octane (2.3 g, 20.7 mmol), water (22 mL), andtetrahydrofuran (45 mL) were placed in a 250 mL reaction flask andstirred to dissolve. Then, the reaction was carried out at 70° C. for 24hours. After the reaction was completed, water was added. Then, anextraction was performed by using ethyl acetate and water, and theorganic phase was collected. The solvent of the collected organic phasewas removed by using a rotary concentrator. Then, column chromatographywas performed to obtain the additive molecule Exp-B1.

The additive molecule Exp-B1 was analyzed by nuclear magnetic resonancespectroscopy, and the obtained spectral information was as follows: ¹HNMR (CDCl₃, 400 MHz): δ 0.29 (s, 3H), 0.80-1.46 (m, 26H), 1.68-1.92 (m,12H), 2.33-2.36 (m, 2H), 2.42-2.45 (m, 1H), 4.15 (t, J=6.8 Hz, 4H), 4.34(d, J=6.4 Hz, 4H), 5.84 (s, 2H), 6.26 (s, 2H), 7.20 (d, J=8.0 Hz, 2H),7.40 (d, J=8.0 Hz, 2H).

Preparation Example 8 Preparing the Additive Molecule Exp-C1

The synthesis flow of the additive molecule Exp-C1 is shown above.Sodium hydride (NaH, 4.2 g, 173 mmol), dimethylformamide (200 mL), andCompound 2 (24.0 g, 49.4 mmol) were placed in a 500 mL double-neckedflask and stirred for 30 minutes. Then, iodoethane (23.1 g, 148.1 mmol)was added at 0° C., and the reaction was carried out at 100° C. for 8hours. After the reaction was completed, water was added. Then, anextraction was performed by using ethyl acetate and water, and theorganic phase was collected. The solvent of the collected organic phasewas removed by using a rotary concentrator. Then, column chromatographywas performed to obtain Compound 22.

Compound 22 (8.0 g, 15.6 mmol) and anhydrous tetrahydrofuran (100 mL)were placed in a 500 mL reaction flask and stirred to dissolve. Then,n-butyllithium (2.5 M, solvent: tetrahydrofuran; 22.4 mL, 56.0 mmol) wasslowly added to the reaction flask at −78° C., and the reaction wascarried out for 1 hour. Next, dimethylchlorosilane (5.3 g, 56.0 mmol)was added to the reaction flask at −78° C., and the reaction was carriedout at room temperature (20-30° C.) for 2 hours. After the reaction wascompleted, dilute hydrochloric acid (1 N, 60 mL) was added. Then, anextraction was performed by using ethyl acetate and water, and theorganic phase was collected. The solvent of the collected organic phasewas removed by using a rotary concentrator. Then, column chromatographywas performed to obtain Compound 23.

Compound 23 (1.0 g, 2.1 mmol), toluene (15 mL) and platinum-containingcatalyst (Pt/C, Pt content: 5 wt %, 0.2 g) were placed in a 100 mLdouble-necked flask, and nitrogen gas was introduced. Then, allylmethacrylate (1.1 g, 8.5 mmol) was added and heated to 100° C. for 8hours to carry out the reaction. After the reaction was completed, theplatinum-containing catalyst was removed by filtration. Then, anextraction was performed by using toluene and water, and the organicphase was collected. The solvent of the collected organic phase wasremoved by using a rotary concentrator. Then, column chromatography wasperformed to obtain the additive molecule Exp-C1.

The additive molecule Exp-C1 was analyzed by nuclear magnetic resonancespectroscopy, and the obtained spectral information was as follows: ¹HNMR (CDCl₃, 400 MHz): δ 0.32 (s, 12H), 0.83-1.45 (m, 29H), 1.65-1.96 (m,18H), 2.39-2.45 (m, 1H), 3.78 (q, J=7.2 Hz, 2H), 4.12 (t, J=6.8 Hz, 4H),5.55 (s, 2H), 6.11 (s, 2H), 7.26 (s, 2H).

Preparation Example 9 Preparing the Additive Molecule Ref

The synthesis flow of the additive molecule Ref is shown above. Theadditive molecule Ref can be synthesized in accordance with theprocedure for synthesizing Compound 16 by using Compound 24 as startingmaterial.

In the following Examples and Reference Examples, all of theliquid-crystal compositions were prepared by forming the mother liquidformed by 100 parts by weight of the molecules of formula (II) inaccordance with Table 4, and then, 0.3 parts by weight of molecule offormula (III) shown in Table 4 was added. Next, the additive moleculesshown in Tables 1-3 or 5 were additionally added to the aboveliquid-crystal composition in accordance with the amount that was added,shown in Table 6. For example, the liquid-crystal composition of Example9 is 100 parts by weight of the mother liquid formed by the molecules offormula (II) shown in Table 4, and 0.3 parts by weight of the moleculeof formula (III), 0.50 parts by weight of the additive molecule Exp-A2,and 0.20 parts by weight of the additive molecule Exp-B 1 is furtheradded. Furthermore, in the liquid-crystal compositions of ReferenceExample and Examples 1-7 shown in Table 6, only one kind of the additivemolecules shown in Tables 1-3 or 5 was added.

Production of the Liquid-Crystal Display Device

In 100 parts by weight of the mother liquid formed by the molecules offormula (II), 0.3 parts by weight of the molecule of formula (III) shownin Table 4 and the additive molecules shown in Tables 1-3 or 5 (theamounts that were added are shown in Table 6) were added, and themixture was uniformly mixed and heated to the clearing point. Then, itwas cooled to room temperature to form a liquid-crystal composition of aReference Example or an Example. The liquid-crystal composition of theExample or the Reference Example is injected between two indium tinoxide (ITO) substrates having an interval of 3.5 μm and having noalignment layer to form the liquid-crystal display element of theExample or the Reference Example, respectively. A DC voltage of 12 V andirradiation of ultraviolet light (peak wavelength: 313 nm) were appliedto the liquid-crystal display element to form the liquid-crystal displaydevice of the Example or the Reference Example.

Properties of the Liquid-Crystal Composition

[Vertical Alignment]

The liquid-crystal display device was disposed in a polarizingmicroscope in which a polarizing element and an analyzer were arrangedorthogonally. The element was irradiated with light from below, and thepresence or absence of light leakage was observed to judge the verticalalignment. The experimental results of vertical alignment were shown inTable 7.

◯: Light does not pass through any part of the element (the whole pieceis uniform and has no light transmission). This result indicates thatthe device has vertical alignment.

Δ: Light passes through a part of the element. This result indicatesthat the device has vertical alignment, but the degree of verticalalignment is lower.

X: Light passes through all parts of the element (the whole piece isuniformly transmitted by light). This result indicates that the devicehas no vertical alignment.

[Voltage Holding Ratio]

A DC voltage (charge voltage of 5 V, operating frequency of 60 Hz) wasapplied to the liquid-crystal display of the Example or the ReferenceExample at an ambient temperature of 60° C. The voltage value V2 afterthe application was released to 1.667 sec was measured by theliquid-crystal physical parameter measuring instrument (product number:ALCT-IV1, manufactured by INSTEC Co., Ltd.). The experimental results ofvoltage holding ratio were shown in Table 7. The formula for calculatingthe voltage holding ratio (VHR) of the liquid-crystal display device isas follows:VHR=(V2/applied voltage value)×100%.

[Stability of the Alignment Ability]

A voltage of 0V to 10V was continuously applied to the liquid-crystaldisplay device, and the light transmittance of the liquid-crystaldisplay device corresponding to different voltages was measured. Thelight transmittance was recorded every 0.1V, and a graph of voltageversus transmittance was drawn based on the experimental results. Thevoltage corresponding to a liquid-crystal display device having atransmittance of 1% is defined as V(th,i). Next, a deteriorationexperiment was performed on the liquid-crystal display device. The stepsof the deterioration experiment are as follows. The liquid-crystaldisplay device was placed in an oven (temperature: 60° C.), and avoltage (AC, 10 V) was applied for a duration of 4 days. After thedeterioration experiment was performed, the liquid-crystal displaydevice was subjected to the experiment described above, and a graph ofvoltage versus transmittance was drawn. The voltage corresponding to aliquid-crystal display device having a transmittance of 1% is defined asV(th,f). The ΔVth value (unit: Volts) of the liquid-crystal displaydevice is calculated according to the following formula. The smaller theabsolute value of ΔVth, the better the stability of the alignmentability of the additive molecules. The experimental results of the ΔVthvalue were shown in Table 7.ΔVth=V(th,f)−V(th,i)

TABLE 6 Amount added Amount added Amount added Additive (parts byAdditive (parts by Additive (parts by molecule weight) molecule weight)molecule weight) Reference Example Ref 1.50 — — — — Example 1 Exp-A10.03 — — — — Example 2 Exp-A2 3.00 — — — — Example 3 Exp-A3 3.00 — — — —Example 4 Exp-A4 1.50 — — — — Example 5 Exp-A5 0.03 — — — — Example 6Exp-A6 0.05 — — — — Example 7 Exp-A6 0.10 — — — — Example 8 Exp-A1 0.03Exp-A2 0.50 — — Example 9 Exp-A2 0.50 Exp-B1 0.20 — — Example 10 Exp-A20.50 Exp-B1 0.50 — — Example 11 Exp-A2 1.00 Exp-B1 0.10 — — Example 12Exp-A3 0.20 Exp-B1 0.10 — — Example 13 Exp-A3 0.50 Exp-B1 0.10 — —Example 14 Exp-A1 0.10 — — Exp-C1 0.50 Example 15 Exp-A4 0.50 Exp-B10.10 — — Example 16 Exp-A6 0.10 — — Exp-C1 3.00 Example 17 Exp-A6 0.05Exp-B1 0.50 — — Example 18 Exp-A2 0.50 Exp-B1 0.20 Exp-C1 0.10 Example19 Exp-A2 0.50 Exp-A6 0.05 Exp-B1 0.10 Example 20 Exp-A6 0.05 Exp-B10.05 Exp-C1 3.00

TABLE 7 Vertical alignment VHR (%) ΔVth value (V) Reference ◯ 37.2 −0.49Example Example 1 Δ 96.0 −0.03 Example 2 Δ 98.1 −0.07 Example 3 ◯ 97.5−0.06 Example 4 ◯ 97.9 −0.03 Example 5 Δ 97.5 −0.09 Example 6 Δ 95.3−0.10 Example 7 ◯ 97.3 −0.08 Example 8 ◯ 95.4 −0.06 Example 9 ◯ 97.2−0.01 Example 10 ◯ 97.6 −0.02 Example 11 ◯ 96.0 −0.08 Example 12 ◯ 92.5−0.17 Example 13 ◯ 96.6 −0.05 Example 14 ◯ 97.0 −0.12 Example 15 ◯ 97.9−0.01 Example 16 ◯ 97.8 −0.04 Example 17 ◯ 97.1 −0.13 Example 18 ◯ 95.6−0.11 Example 19 ◯ 97.7 −0.02 Example 20 ◯ 97.5 −0.07

Referring to the Reference Example of Table 7, the Reference Exampleincludes the additive molecule Ref. Because the additive molecule Refdoes not have the silicon atom and the polymerizable group, the voltageholding ratio of the liquid-crystal composition of the Reference Exampleis not good. Furthermore, because the additive molecule Ref does nothave the polymerizable group, the stability of the vertical alignmentability of the liquid-crystal composition of the Reference Example isnot good.

Referring to Examples 1-20 of Table 7, each of Examples 1-20 includes atleast one first additive molecule represented by formula (I) or formula(I′). The results show that the liquid-crystal molecules of Examples1-20 are all vertically aligned. In Example 2, only one first additivemolecule (i.e., the additive molecule Exp-A2) is used. The additivemolecule Exp-A2 does not have the anchoring group, so it is difficultfor the additive molecule Exp-A2 to be fixed on the substratevertically. As a result, the degree of vertical alignment of theliquid-crystal molecules is not good. However, the degree of verticalalignment of liquid-crystal molecules can be improved by adding otheradditive molecules having an anchoring group. For example, in Examples8-11, the additive molecule Exp-A2 and at least one other additivemolecule (i.e., the additive molecule Exp-A1 or the additive moleculeExp-B1) are used together. The additive molecule Exp-A1 and the additivemolecule Exp-B1 both have anchor groups, and can improve the degree ofvertical alignment of liquid-crystal molecules, as shown in Table 7.

In Examples 1, 5, and 6, because the amount of first additive molecules(i.e., the additive molecule Exp-A1, the additive molecule Exp-A5, andthe additive molecule Exp-A6) that are added is too low, the degree ofvertical alignment of the liquid-crystal molecules is not good. Thedegree of vertical alignment of the liquid-crystal molecules can beimproved by adjusting the amount that is added. For example, in Example4, by adjusting the amount of additive molecules that are added to 1.5parts by weight, the degree of vertical alignment of the liquid-crystalmolecules can be improved, as shown in Table 7. Furthermore, the degreeof vertical alignment of the liquid-crystal molecules can also beimproved by adding other additive molecules having the anchoring group.For example, in Example 8, by using the additive molecule Exp-A1 and theadditive molecule Exp-A2 together, the degree of vertical alignment ofthe liquid-crystal molecules can be improved, as shown in Table 7.

Referring to Examples 1-20 of Table 7, each of Examples 1-20 includes atleast one first additive molecule represented by formula (I) or formula(I′). In these first additive molecules, the rightmost cyclic functionalgroup of the main chain of the molecule include a side chain functionalgroup at its opposite sides, respectively. Each of these side chainfunctional groups includes at least one cyclic functional group and atleast one polymerizable group. The results show that each of theabsolute values of ΔVth of Examples 1-20 is very small. In particular,in Examples 1-7, only one first additive molecule is used. The absolutevalue of ΔVth in each of Examples 1-7 is smaller than or equal to 0.10V. It can be proved that the first additive molecule can significantlyimprove the stability of the vertical alignment ability of theliquid-crystal molecules.

Referring to Examples 1-20 of Table 7, each of Examples 1-20 includes atleast one first additive molecule represented by formula (I) or formula(I′). The results show that the voltage holding ratio is greater than90% in each of Examples 1-20. In particular, in Examples 1-7, only onefirst additive molecule is used. The voltage holding ratio is greaterthan 95% in each of Examples 1-7. It can be proved that the firstadditive molecule can significantly improve the voltage holding ratio.

Referring to Example 8 of Table 7, the first additive molecule havingthe anchoring group (i.e., the additive molecule Exp-A1) and the firstadditive molecule having no anchoring group (i.e., the additive moleculeExp-A2) are used together. The results show that the degree of verticalalignment, the stability of the vertical alignment ability, and thevoltage holding ratio of the liquid-crystal molecules can besignificantly improved by merely adding 0.53 parts by weight of theadditive molecule.

Referring to Examples 9-13 of Table 7, the first additive moleculehaving no anchoring group (i.e., the additive molecule Exp-A2 or theadditive molecule Exp-A3) and the second additive molecule having theanchoring group (i.e., the additive molecule Exp-B1) are used together.The results show that the degree of vertical alignment, the stability ofthe vertical alignment ability, and the voltage holding ratio of theliquid-crystal molecules can be significantly improved by merely addinga few amount (for example, the total amount smaller than 1.20 parts byweight) of the additive molecule.

Referring to Examples 7 and 16 of Table 7, the kind of first additivemolecule, and the amount of it that is added, is the same. In Example16, the third additive molecule having the polymerizable group (i.e.,the additive molecule Exp-C1) is added. The results show that thestability of the vertical alignment ability and the voltage holdingratio of the liquid-crystal molecules can be further improved.

In summary, the additive molecule of the present disclosure can haveexcellent stability of the vertical alignment ability while having ahigh voltage holding ratio. By adding the above-mentioned additivemolecule to the liquid-crystal composition, it is possible to realize astate in which most of the liquid-crystal molecules are verticallyaligned stably and well without using a conventional alignment film. Inorder to balance the degree of vertical alignment and the stability ofthe alignment ability of the liquid-crystal composition, the content ofthe first additive molecule may be adjusted, or two or more kinds ofadditive molecules may be used together. Furthermore, the liquid-crystaldisplay device using the additive molecules of the embodiments of thepresent disclosure can have a high voltage retention rate (for example,the voltage retention rate greater than 90%) and excellent stability ofthe alignment ability. As a result, the performance and durability ofthe liquid-crystal display device can be significantly improved.

Although the disclosure has been described by way of example and interms of the preferred embodiments, it should be understood that variousmodifications and similar arrangements (as would be apparent to thoseskilled in the art) can be made herein without departing from the spiritand scope of the disclosure as defined by the appended claims.

What is claimed is:
 1. An additive, comprising: a first additivemolecule, wherein the first additive molecule has a structurerepresented by formula (I):

wherein, in formula (I), R^(i1) represents fluorine, chlorine, hydrogen,a C₁-C₂₀ linear alkyl group, a C₃-C₂₀ branched alkyl group, a C₁-C₂₀linear alkoxy group, or a C₃-C₂₀ branched alkoxy group, wherein theC₁-C₂₀ linear alkyl group, the C₃-C₂₀ branched alkyl group, the C₁-C₂₀linear alkoxy group, or the C₃-C₂₀ branched alkoxy group isunsubstituted or at least one —CH₂— of the C₁-C₂₀ linear alkyl group,the C₃-C₂₀ branched alkyl group, the C₁-C₂₀ linear alkoxy group, or theC₃-C₂₀ branched alkoxy group is substituted by —C≡C—, —CH═CH—, —CF₂O—,—O—, —COO—, —OCO—, or —OOC—, and/or at least one hydrogen atom of theC₁-C₂₀ linear alkyl group, the C₃-C₂₀ branched alkyl group, the C₁-C₂₀linear alkoxy group, or the C₃-C₂₀ branched alkoxy group is substitutedby a halogen atom; A^(i1) represents a 1,4-phenylene group, a1,4-cyclohexylene group, a benzofuran-2,5-diyl group, a1,3-dioxane-2,5-diyl group, a tetrahydropyran-2,5-diyl group, a divalentdioxabicyclo[2.2.2]octylene group, a divalenttrioxabicyclo[2.2.2]octylene group, a tetrahydronaphthalene-2,6-diylgroup, a 1,3-cyclopentylene, a 1,3-cyclobutylene, or an indane-2,5-diylgroup, wherein the 1,4-phenylene group, the 1,4-cyclohexylene group, thetetrahydronaphthalene-2,6-diyl group, the 1,3-cyclopentylene, thebenzofuran-2,5-diyl group, the 1,3-cyclobutylene, or the indane-2,5-diylgroup is unsubstituted or at least one hydrogen atom of the1,4-phenylene group, the 1,4-cyclohexylene group, thetetrahydronaphthalene-2,6-diyl group, the 1,3-cyclopentylene, thebenzofuran-2,5-diyl group, the 1,3-cyclobutylene, or the indane-2,5-diylgroup is substituted by a halogen atom, —CH₃, —CH₂CH₃, or a —CN group,and/or at least one —CH₂— of the 1,4-phenylene group, the1,4-cyclohexylene group, the tetrahydronaphthalene-2,6-diyl group, the1,3-cyclopentylene, the benzofuran-2,5-diyl group, the1,3-cyclobutylene, or the indane-2,5-diyl group is substituted by —O—,—N— or —S—, and wherein the —O—, —N—, and —S— do not directly bond toone another; A^(i2) represents a 1,4-phenylene group, a1,4-cyclohexylene group, a benzofuran-2,5-diyl group, atetrahydronaphthalene-2,6-diyl group, or an indane-2,5-diyl group,wherein the 1,4-phenylene group, the 1,4-cyclohexylene group, thetetrahydronaphthalene-2,6-diyl group, the benzofuran-2,5-diyl group, orthe indane-2,5-diyl group is unsubstituted or at least one hydrogen atomof the 1,4-phenylene group, the 1,4-cyclohexylene group, thetetrahydronaphthalene-2,6-diyl group, the benzofuran-2,5-diyl group, orthe indane-2,5-diyl group is substituted by a halogen atom, —CH₃,—CH₂CH₃, or a —CN group, and/or at least one —CH₂— of the 1,4-phenylenegroup, the 1,4-cyclohexylene group, the tetrahydronaphthalene-2,6-diylgroup, the benzofuran-2,5-diyl group, or the indane-2,5-diyl group issubstituted by —O—, —N— or —S—, and wherein the —O—, —N—, and —S— do notdirectly bond to one another; Z^(i) represents a single bond, a C₁-C₁₅alkylene group, a C₁-C₁₅ alkyleneoxy group, —C≡C—, —CH═CH—, —CF₂O—,—OCF₂—, —COO—, —OCO—, —OOC—, —CF₂—CF₂—, or —CF═CF—; m¹ represents 1, 2,3, or 4, and when m¹ represents 2, 3, or 4, the two or more A^(i1)groups are identical to each other or different from each other, and thetwo or more Z^(i) groups are identical to each other or different fromeach other; m² represents 1, 2, or 3, and when m² represents 2 or 3, thetwo or more R^(i2) groups are identical to each other or different fromeach other; R^(i2) represents a structure represented by formula (Ia),formula (Ib), or formula (Ic), and at least one R^(i2) represents thestructure represented by formula (Ib) or formula (Ic):

and R^(i3) represents a structure represented by formula (Id), formula(Ie), or formula (If):

wherein, in formula (Ia), formula (Ib), formula (Ic), formula (Id),formula (Ie), and formula (If), A^(i3) represents a 1,4-phenylene group,a 1,4-cyclohexylene group, a 1,3-cyclopentylene, or a 1,3-cyclobutylene,wherein the 1,4-phenylene group, the 1,4-cyclohexylene group, the1,3-cyclopentylene, or the 1,3-cyclobutylene is unsubstituted or atleast one hydrogen atom of the 1,4-phenylene group, the1,4-cyclohexylene group, the 1,3-cyclopentylene, or the1,3-cyclobutylene is substituted by a halogen atom, —CH₃, —CH₂CH₃, or a—CN group, and/or at least one —CH═ of the 1,4-phenylene group, the1,4-cyclohexylene group, the 1,3-cyclopentylene, or the1,3-cyclobutylene is substituted by —N═, and/or at least one —CH₂— ofthe 1,4-phenylene group, the 1,4-cyclohexylene group, the1,3-cyclopentylene, or the 1,3-cyclobutylene is substituted by —O—,—NR^(e)— or —S—, and wherein the —O—, —NR^(e)—, and —S— do not directlybond to one another, wherein R^(e) represents hydrogen, a C₁-C₄ linearalkyl group, or a C₃-C₄ branched alkyl group; each of R^(i4), R^(i5),and R^(i6) independently represents fluorine, chlorine, hydrogen, aC₁-C₂₀ linear alkyl group, a C₃-C₂₀ branched alkyl group, a C₁-C₂₀linear alkoxy group, or a C₃-C₂₀ branched alkoxy group, wherein theC₁-C₂₀ linear alkyl group, the C₃-C₂₀ branched alkyl group, the C₁-C₂₀linear alkoxy group, or the C₃-C₂₀ branched alkoxy group isunsubstituted or at least one —CH₂— of the C₁-C₂₀ linear alkyl group,the C₃-C₂₀ branched alkyl group, the C₁-C₂₀ linear alkoxy group, or theC₃-C₂₀ branched alkoxy group is substituted by —C≡C—, —CH═CH—, —CF₂O—,—O—, —COO—, —OCO—, or —OOC—, and/or at least one hydrogen atom of theC₁-C₂₀ linear alkyl group, the C₃-C₂₀ branched alkyl group, the C₁-C₂₀linear alkoxy group, or the C₃-C₂₀ branched alkoxy group is substitutedby a halogen atom; each of L^(i1), L^(i2), L^(i3), L^(i4), L^(i5),L^(i6), L^(i7), L^(i8), L^(i9), and L^(i10) independently represents asingle bond, a C₁-C₁₅ linear alkylene group, a C₃-C₁₅ branched alkylenegroup, a C₁-C₁₅ linear alkyleneoxy group, or a C₃-C₁₅ branchedalkyleneoxy group, wherein the C₁-C₁₅ linear alkylene group, the C₃-C₁₅branched alkylene group, the C₁-C₁₅ linear alkyleneoxy group, or theC₃-C₁₅ branched alkyleneoxy group is unsubstituted or at least one —CH₂—of the C₁-C₁₅ linear alkylene group, the C₃-C₁₅ branched alkylene group,the C₁-C₁₅ linear alkyleneoxy group, or the C₃-C₁₅ branched alkyleneoxygroup is substituted by —C≡C—, —CH═CH—, —CF₂O—, —SiR^(a) ₂—, —O—, —CO—,—COO—, —OCO—, or —OOC—, and/or at least one hydrogen atom of the C₁-C₁₅linear alkylene group, the C₃-C₁₅ branched alkylene group, the C₁-C₁₅linear alkyleneoxy group, or the C₃-C₁₅ branched alkyleneoxy group issubstituted by a halogen atom, and wherein R^(a) represents a C₁-C₁₀linear alkyl group or a C₃-C₁₀ branched alkyl group, and two R^(a)groups bonded to the same Si atom are identical to each other ordifferent from each other; m³ represents 1 or 2, and when m³ represents2, the two A^(i3) groups are identical to each other or different fromeach other, and the two L^(i3) groups are identical to each other ordifferent from each other; m⁴ represents 1 or 2, and when m⁴ represents2, the two A^(i3) groups are identical to each other or different fromeach other, and the two L⁵ groups are identical to each other ordifferent from each other; m⁵+m⁶=3, m⁵ represents 2 or 3, and the two ormore L^(i6) groups are identical to each other or different from eachother, and the two or more X^(i3) groups are identical to each other ordifferent from each other; m⁷+m⁸=3, m⁷ represents 2 or 3, and the two ormore L^(i10) groups are identical to each other or different from eachother, and the two or more X^(i5) groups are identical to each other ordifferent from each other; each of X^(i1), X^(i2), and X^(i3)independently represents hydrogen, —OH,

and each of X^(i4) and X^(i5) independently represents hydrogen, —OH,

wherein at least one of X^(i2) and X^(i3) represents

and wherein Y^(i1) represents —OH, a C₁-C₁₅ alkyl group, or a C₂-C₁₅alkenyl group, and at least one hydrogen atom of the C₁-C₁₅ alkyl groupor the C₂-C₁₅ alkenyl group is substituted by —OH; Y^(i2) representshydrogen, halogen, a C₁-C₁₅ alkyl group, or a C₂-C₁₅ alkenyl group,wherein the C₁-C₁₅ alkyl group or the C₂-C₁₅ alkenyl group isunsubstituted or at least one hydrogen atom of the C₁-C₁₅ alkyl group orthe C₂-C₁₅ alkenyl group is substituted by a halogen atom.
 2. Theadditive as claimed in claim 1, wherein the first additive molecule hasa structure represented by formula (I′):

wherein, in formula (I′), R^(i1) represents fluorine, chlorine,hydrogen, a C₁-C₁₂ linear alkyl group, a C₃-C₁₂ branched alkyl group, aC₁-C₁₂ linear alkoxy group, or a C₃-C₁₂ branched alkoxy group, whereinthe C₁-C₁₂ linear alkyl group, the C₃-C₁₂ branched alkyl group, theC₁-C₁₂ linear alkoxy group, or the C₃-C₁₂ branched alkoxy group isunsubstituted or at least one —CH₂— of the C₁-C₁₂ linear alkyl group,the C₃-C₁₂ branched alkyl group, the C₁-C₁₂ linear alkoxy group, or theC₃-C₁₂ branched alkoxy group is substituted by —C≡C—, —CH═CH—, —CF₂O—,—O—, —COO—, —OCO—, or —OOC—, and/or at least one hydrogen atom of theC₁-C₁₂ linear alkyl group, the C₃-C₁₂ branched alkyl group, the C₁-C₁₂linear alkoxy group, or the C₃-C₁₂ branched alkoxy group is substitutedby a halogen atom; the definitions of A^(i1) and Z^(i) are respectivelythe same as the definitions of A^(i1) and Z^(i) defined in claim 1; andm¹ represents 0, 1, 2, 3, or 4, and when m¹ represents 2, 3, or 4, thetwo or more A^(i1) groups are identical to each other or different fromeach other, and the two or more Z^(i) groups are identical to each otheror different from each other; R^(i2) represents a structure representedby formula (Ia), formula (Ib), or formula (Ic), and at least one R^(i2)represents the structure represented by formula (Ib) or formula (Ic):

and R^(i3) represents a structure represented by formula (Id), formula(Ie), or formula (If):

wherein, in formula (Ia), formula (Ib), formula (Ic), formula (Id),formula (Ie), and formula (If), each of R^(i4), R^(i5), and R^(i6)independently represents fluorine, chlorine, hydrogen, a C₁-C₁₂ linearalkyl group, a C₃-C₁₂ branched alkyl group, a C₁-C₁₂ linear alkoxygroup, or a C₃-C₁₂ branched alkoxy group, wherein the C₁-C₁₂ linearalkyl group, the C₃-C₁₂ branched alkyl group, the C₁-C₁₂ linear alkoxygroup, or the C₃-C₁₂ branched alkoxy group is unsubstituted or at leastone —CH₂— of the C₁-C₁₂ linear alkyl group, the C₃-C₁₂ branched alkylgroup, the C₁-C₁₂ linear alkoxy group, or the C₃-C₁₂ branched alkoxygroup is substituted by —C≡C—, —CH═CH—, —CF₂O—, —O—, —COO—, —OCO—, or—OOC—, and/or at least one hydrogen atom of the C₁-C₁₂ linear alkylgroup, the C₃-C₁₂ branched alkyl group, the C₁-C₁₂ linear alkoxy group,or the C₃-C₁₂ branched alkoxy group is substituted by a halogen atom;the definitions of L^(i1), L^(i2), L^(i3), L^(i4), L^(i5), L^(i6),L^(i7), L^(i8), L^(i9), L^(i10), A^(i3), m³, m⁴, m⁵, m⁶, m⁷, and m⁸ arerespectively the same as the definitions of L^(i1), L^(i2), L^(i3),L^(i4), L^(i5), L^(i6), L^(i7), L^(i8), L^(i9), L^(i10), A^(i3), m³, m⁴,m⁵, m⁶, m⁷, and m⁸ defined in claim 1; each of X^(i1), X^(i2), X^(i3),X^(i4) and X^(i5) independently represents hydrogen, —OH,

wherein at least one of X^(i2) and X^(i3) represents

and wherein Y^(i1) represents —OH, a C₁-C₁₀ alkyl group, or a C₂-C₁₀alkenyl group, and at least one hydrogen atom of the C₁-C₁₀ alkyl groupor the C₂-C₁₀ alkenyl group is substituted by —OH; and Y^(i2) representshydrogen, halogen, a C₁-C₁₀ alkyl group, or a C₂-C₁₀ alkenyl group,wherein the C₁-C₁₀ alkyl group or the C₂-C₁₀ alkenyl group isunsubstituted or at least one hydrogen atom of the C₁-C₁₀ alkyl group orthe C₂-C₁₀ alkenyl group is substituted by a halogen atom.
 3. Theadditive as claimed in claim 2, further comprising a second additivemolecule, wherein the second additive molecule has a structurerepresented by formula (I-1):

wherein, in formula (I-1), R¹ represents fluorine, chlorine, hydrogen, aC₁-C₁₅ linear alkyl group, a C₃-C₁₅ branched alkyl group, a C₁-C₁₅linear alkoxy group, or a C₃-C₁₅ branched alkoxy group, wherein theC₁-C₁₅ linear alkyl group, the C₃-C₁₅ branched alkyl group, the C₁-C₁₅linear alkoxy group, or the C₃-C₁₅ branched alkoxy group isunsubstituted or at least one —CH₂— of the C₁-C₁₅ linear alkyl group,the C₃-C₁₅ branched alkyl group, the C₁-C₁₅ linear alkoxy group, or theC₃-C₁₅ branched alkoxy group is substituted by —CH═CH—, —CF₂O—, —O—,—COO—, —OCO—, or —OOC—, and/or at least one hydrogen atom of the C₁-C₁₅linear alkyl group, the C₃-C₁₅ branched alkyl group, the C₁-C₁₅ linearalkoxy group, or the C₃-C₁₅ branched alkoxy group is substituted by ahalogen atom; A¹ represents a 1,4-phenylene group, a 1,4-cyclohexylenegroup, a benzofuran-2,5-diyl group, a 1,3-dioxane-2,5-diyl group, atetrahydropyran-2,5-diyl group, a divalent dioxabicyclo[2.2.2]octylenegroup, a divalent trioxabicyclo[2.2.2]octylene group, atetrahydronaphthalene-2,6-diyl group, a 1,3-cyclopentylene, a1,3-cyclobutylene, or an indane-2,5-diyl group, wherein the1,4-phenylene group, the 1,4-cyclohexylene group, thetetrahydronaphthalene-2,6-diyl group, the 1,3-cyclopentylene, the1,3-cyclobutylene, or the indane-2,5-diyl group is unsubstituted or atleast one hydrogen atom of the 1,4-phenylene group, the1,4-cyclohexylene group, the tetrahydronaphthalene-2,6-diyl group, the1,3-cyclopentylene, the 1,3-cyclobutylene, or the indane-2,5-diyl groupis substituted by a halogen atom, —CH₃, —CH₂CH₃, or a —CN group, and/orat least one —CH₂— of the 1,4-phenylene group, the 1,4-cyclohexylenegroup, the tetrahydronaphthalene-2,6-diyl group, the 1,3-cyclopentylene,the 1,3-cyclobutylene, or the indane-2,5-diyl group is substituted by—O—, —N— or —S—, and wherein the —O—, —N—, and —S— do not directly bondto one another; A² represents a 1,4-phenylene group, a 1,4-cyclohexylenegroup, a benzofuran-2,5-diyl group, or an indane-2,5-diyl group, whereinthe 1,4-phenylene group, the 1,4-cyclohexylene group, thebenzofuran-2,5-diyl group, or the indane-2,5-diyl group is unsubstitutedor at least one hydrogen atom of the 1,4-phenylene group, the1,4-cyclohexylene group, the benzofuran-2,5-diyl group, or theindane-2,5-diyl group is substituted by a halogen atom, —CH₃, —CH₂CH₃,or a —CN group, and/or at least one —CH₂— of the 1,4-phenylene group,the 1,4-cyclohexylene group, the benzofuran-2,5-diyl group, or theindane-2,5-diyl group is substituted by —O—, —N— or —S—, and wherein the—O—, —N—, and —S— do not directly bond to one another; Z¹ represents asingle bond, a C₁-C₁₅ alkylene group, a C₁-C₁₅ alkyleneoxy group, —C≡C—,—CH═CH—, —CF₂O—, —OCF₂—, —COO—, —OCO—, —OOC—, —CF₂—CF₂—, or —CF═CF—; n¹represents 1, 2, or 3, and when n¹ represents 2 or 3, the two or more A¹groups are identical to each other or different from each other, and thetwo or more Z¹ groups are identical to each other or different from eachother; n² represents 0 or 1; and K¹ represents a structure representedby formula (I-1-a), formula (I-1-b), or formula (I-1-c):

wherein, in formula (I-1-a), formula (I-1-b), and formula (I-1-c), eachof L² and L³ independently represents a single bond, a C₁-C₁₅ linearalkylene group, a C₃-C₁₅ branched alkylene group, a C₁-C₁₅ linearalkyleneoxy group, or a C₃-C₁₅ branched alkyleneoxy group, wherein theC₁-C₁₅ linear alkylene group, the C₃-C₁₅ branched alkylene group, theC₁-C₁₅ linear alkyleneoxy group, or the C₃-C₁₅ branched alkyleneoxygroup is unsubstituted or at least one —CH₂— of the C₁-C₁₅ linearalkylene group, the C₃-C₁₅ branched alkylene group, the C₁-C₁₅ linearalkyleneoxy group, or the C₃-C₁₅ branched alkyleneoxy group issubstituted by —C≡C—, —CH═CH—, —CF₂O—, —SiR^(a) ₂—, —O—, —COO—, —OCO—,or —OOC—, and/or at least one hydrogen atom of the C₁-C₁₅ linearalkylene group, the C₃-C₁₅ branched alkylene group, the C₁-C₁₅ linearalkyleneoxy group, or the C₃-C₁₅ branched alkyleneoxy group issubstituted by a halogen atom, and wherein R^(a) represents a C₁-C₁₀linear alkyl group or a C₃-C₁₀ branched alkyl group, and two R^(a)groups bonded to the same Si atom are identical to each other ordifferent from each other; each of R², R³ and R⁴ independentlyrepresents fluorine, chlorine, hydrogen, a C₁-C₈ linear alkyl group, aC₃-C₈ branched alkyl group, a C₁-C₈ linear alkoxy group, or a C₃-C₈branched alkoxy group, wherein the C₁-C₈ linear alkyl group, the C₃-C₈branched alkyl group, the C₁-C₈ linear alkoxy group, or the C₃-C₈branched alkoxy group is unsubstituted or at least one —CH₂— of theC₁-C₈ linear alkyl group, the C₃-C₈ branched alkyl group, the C₁-C₈linear alkoxy group, or the C₃-C₈ branched alkoxy group is substitutedby —CH═CH—, —CF₂O—, —O—, —COO—, —OCO—, or —OOC—, and/or at least onehydrogen atom of the C₁-C₈ linear alkyl group, the C₃-C₈ branched alkylgroup, the C₁-C₈ linear alkoxy group, or the C₃-C₈ branched alkoxy groupis substituted by a halogen atom; n³+n⁴=3, n⁴ represents 2 or 3, and thetwo or more L² groups are identical to each other or different from eachother, and the two or more X¹ groups are identical to each other ordifferent from each other; n⁵+n⁶=3, n⁶ represents 2 or 3, and the two ormore L² groups are identical to each other or different from each other,and the two or more X² groups are identical to each other or differentfrom each other; each of X¹ and X² independently represents

wherein Y¹ represents —OH, a C₁-C₈ alkyl group, or a C₂-C₈ alkenylgroup, and at least one hydrogen atom of the C₁-C₈ alkyl group or theC₂-C₈ alkenyl group is substituted by —OH; Y² represents hydrogen,halogen, a C₁-C₈ alkyl group, or a C₂-C₈ alkenyl group, wherein theC₁-C₈ alkyl group or the C₂-C₈ alkenyl group is unsubstituted or atleast one hydrogen atom of the C₁-C₈ alkyl group or the C₂-C₈ alkenylgroup is substituted by a halogen atom; K² represents a structurerepresented by formula (I-1-d), formula (I-1-e), or formula (I-1-f):

and K³ represents a structure represented by formula (I-1-g) or formula(I-1-h):

wherein, in formula (I-1-d), formula (I-1-e), formula (I-1-f), formula(I-1-g), and formula (I-1-h), each of L¹, L², L³, L⁴, L⁵, L⁶, and L⁷independently represents a single bond, a C₁-C₁₅ linear alkylene group,a C₃-C₁₅ branched alkylene group, a C₁-C₁₅ linear alkyleneoxy group, ora C₃-C₁₅ branched alkyleneoxy group, wherein the C₁-C₁₅ linear alkylenegroup, the C₃-C₁₅ branched alkylene group, the C₁-C₁₅ linear alkyleneoxygroup, or the C₃-C₁₅ branched alkyleneoxy group is unsubstituted or atleast one —CH₂— of the C₁-C₁₅ linear alkylene group, the C₃-C₁₅ branchedalkylene group, the C₁-C₁₅ linear alkyleneoxy group, or the C₃-C₁₅branched alkyleneoxy group is substituted by —C≡C—, —CH═CH—, —CF₂O—,—SiR^(a) ₂—, —O—, —COO—, —OCO—, or —OOC—, and/or at least one hydrogenatom of the C₁-C₁₅ linear alkylene group, the C₃-C₁₅ branched alkylenegroup, the C₁-C₁₅ linear alkyleneoxy group, or the C₃-C₁₅ branchedalkyleneoxy group is substituted by a halogen atom, and wherein R^(a)represents a C₁-C₁₀ linear alkyl group or a C₃-C₁₀ branched alkyl group,and two R^(a) groups bonded to the same Si atom are identical to eachother or different from each other; each of R², R³, R⁴, R⁵ and R⁶independently represents fluorine, chlorine, hydrogen, a C₁-C₁₀ linearalkyl group, a C₃-C₁₀ branched alkyl group, a C₁-C₁₀ linear alkoxygroup, or a C₃-C₁₀ branched alkoxy group, wherein the C₁-C₁₀ linearalkyl group, the C₃-C₁₀ branched alkyl group, the C₁-C₁₀ linear alkoxygroup, or the C₃-C₁₀ branched alkoxy group is unsubstituted or at leastone —CH₂— of the C₁-C₁₀ linear alkyl group, the C₃-C₁₀ branched alkylgroup, the C₁-C₁₀ linear alkoxy group, or the C₃-C₁₀ branched alkoxygroup is substituted by —C≡C—, —CH═CH—, —CF₂O—, —O—, —COO—, —OCO—, or—OOC—, and/or at least one hydrogen atom of the C₁-C₁₀ linear alkylgroup, the C₃-C₁₀ branched alkyl group, the C₁-C₁₀ linear alkoxy group,or the C₃-C₁₀ branched alkoxy group is substituted by a halogen atom;n⁹+n¹⁰=3, n¹⁰ represents 2 or 3, and the two or more L⁷ groups areidentical to each other or different from each other, and the two ormore X⁴ groups are identical to each other or different from each other;n¹² represents 1, 2, or 3, n¹¹+n¹²=3, and when n¹² represents 2 or 3,the two or more L² groups are identical to each other or different fromeach other, and the two or more X⁵ groups are identical to each other ordifferent from each other; when n¹¹ represents 2, the two R² groups areidentical to each other or different from each other; and n¹⁴ represents1, 2, or 3, n¹³+n¹⁴=3, and when n¹⁴ represents 2 or 3, the two or moreL² groups are identical to each other or different from each other, andthe two or more X⁶ groups are identical to each other or different fromeach other; when n¹³ represents 2, the two R⁴ groups are identical toeach other or different from each other; each of X³, X⁴, X⁵ and X⁶independently represents hydrogen, —OH,

wherein, when K¹ represents the structure represented by formula (I-1-a)or formula (I-1-b), at least one of X¹ and X² represents

when K¹ represents the structure represented by formula (I-1-c), and K²represents the structure represented by formula (I-1-d), at least one ofX⁵ and X⁶ represents

when K¹ represents the structure represented by formula (I-1-c), and K²represents the structure represented by formula (I-1-e) or formula(I-1-f), at least one of X³, X⁴, X⁵ and X⁶ represents


4. The additive as claimed in claim 3, wherein when an amount of thefirst additive molecule is set to 1 part by weight, an amount of thesecond additive molecule is 0.01-60 parts by weight.
 5. The additive asclaimed in claim 3, further comprising a third additive molecule,wherein the third additive molecule has a structure represented byformula (I-1):

wherein in formula (I-1), the definitions of R¹, A¹, A², Z¹, n¹, and n²defined in claim 3; and K¹ represents a structure represented by formula(I-1-a), formula (I-1-b), or formula (I-1-c):

wherein, in formula (I-1-a), formula (I-1-b), and formula (I-1-c), thedefinitions of L², L³, R², R³, R⁴, n³, n⁴, n⁵, and n⁶ are respectivelythe same as the definitions of L², L³, R², R³, R⁴, n³, n⁴, n⁵, and n⁶defined in claim 3; each of X¹ and X² independently represents

and the definitions of Y¹ and Y² are respectively the same as thedefinitions of Y¹ and Y² defined in claim 3; K² represents a structurerepresented by formula (I-1-d), formula (I-1-e), or formula (I-1-f):

and K³ represents a structure represented by formula (I-1-g) or formula(I-1-h):

wherein, in formula (I-1-d), formula (I-1-e), formula (I-1-f), formula(I-1-g), and formula (I-1-h), the definitions of L¹, L², L³, L⁴, L⁵, L⁶,L⁷, R², R³, R⁴, R⁵, R⁶, n⁹, n¹⁰, n¹¹, n¹², n¹³, and n¹⁴ are respectivelythe same as the definitions of L¹, L², L³, L⁴, L⁵, L⁶, L⁷, R², R³, R⁴,R⁵, R⁶, n⁹, n¹⁰, n¹¹, n¹², n¹³, and n¹⁴ defined in claim 3; each of X³,X⁴, X⁵ and X⁶ independently represents hydrogen, —OH,

wherein, when K¹ represents the structure represented by formula (I-1-a)or formula (I-1-b), each of X¹ and X² independently represents

when K¹ represents the structure represented by formula (I-1-c), each ofX³, X⁴, X⁵ and X⁶ represents hydrogen or


6. The additive as claimed in claim 5, wherein when an amount of thefirst additive molecule is set to 1 part by weight, an amount of thesecond additive molecule is 0.01-60 parts by weight, and an amount ofthe third additive molecule is 0.01-80 parts by weight.
 7. The additiveas claimed in claim 2, further comprising a third additive molecule,wherein the third additive molecule has a structure represented byformula (I-1):

wherein, in formula (I-1), R¹ represents fluorine, chlorine, hydrogen, aC₁-C₁₅ linear alkyl group, a C₃-C₁₅ branched alkyl group, a C₁-C₁₅linear alkoxy group, or a C₃-C₁₅ branched alkoxy group, wherein theC₁-C₁₅ linear alkyl group, the C₃-C₁₅ branched alkyl group, the C₁-C₁₅linear alkoxy group, or the C₃-C₁₅ branched alkoxy group isunsubstituted or at least one —CH₂— of the C₁-C₁₅ linear alkyl group,the C₃-C₁₅ branched alkyl group, the C₁-C₁₅ linear alkoxy group, or theC₃-C₁₅ branched alkoxy group is substituted by —CH═CH—, —CF₂O—, —O—,—COO—, —OCO—, or —OOC—, and/or at least one hydrogen atom of the C₁-C₁₅linear alkyl group, the C₃-C₁₅ branched alkyl group, the C₁-C₁₅ linearalkoxy group, or the C₃-C₁₅ branched alkoxy group is substituted by ahalogen atom; A¹ represents a 1,4-phenylene group, a 1,4-cyclohexylenegroup, a benzofuran-2,5-diyl group, a 1,3-dioxane-2,5-diyl group, atetrahydropyran-2,5-diyl group, a divalent dioxabicyclo[2.2.2]octylenegroup, a divalent trioxabicyclo[2.2.2]octylene group, atetrahydronaphthalene-2,6-diyl group, a 1,3-cyclopentylene, a1,3-cyclobutylene, or an indane-2,5-diyl group, wherein the1,4-phenylene group, the 1,4-cyclohexylene group, thetetrahydronaphthalene-2,6-diyl group, the 1,3-cyclopentylene, the1,3-cyclobutylene, or the indane-2,5-diyl group is unsubstituted or atleast one hydrogen atom of the 1,4-phenylene group, the1,4-cyclohexylene group, the tetrahydronaphthalene-2,6-diyl group, the1,3-cyclopentylene, the 1,3-cyclobutylene, or the indane-2,5-diyl groupis substituted by a halogen atom, —CH₃, —CH₂CH₃, or a —CN group, and/orat least one —CH₂— of the 1,4-phenylene group, the 1,4-cyclohexylenegroup, the tetrahydronaphthalene-2,6-diyl group, the 1,3-cyclopentylene,the 1,3-cyclobutylene, or the indane-2,5-diyl group is substituted by—O—, —N— or —S—, and wherein the —O—, —N—, and —S— do not directly bondto one another; A² represents a 1,4-phenylene group, a 1,4-cyclohexylenegroup, a benzofuran-2,5-diyl group, or an indane-2,5-diyl group, whereinthe 1,4-phenylene group, the 1,4-cyclohexylene group, thebenzofuran-2,5-diyl group, or the indane-2,5-diyl group is unsubstitutedor at least one hydrogen atom of the 1,4-phenylene group, the1,4-cyclohexylene group, the benzofuran-2,5-diyl group, or theindane-2,5-diyl group is substituted by a halogen atom, —CH₃, —CH₂CH₃,or a —CN group, and/or at least one —CH₂— of the 1,4-phenylene group,the 1,4-cyclohexylene group, the benzofuran-2,5-diyl group, or theindane-2,5-diyl group is substituted by —O—, —N— or —S—, and wherein the—O—, —N—, and —S— do not directly bond to one another; Z¹ represents asingle bond, a C₁-C₁₅ alkylene group, a C₁-C₁₅ alkyleneoxy group, —C≡C—,—CH═CH—, —CF₂O—, —OCF₂—, —COO—, —OCO—, —OOC—, —CF₂—CF₂—, or —CF═CF—; n¹represents 1, 2, or 3, and when n¹ represents 2 or 3, the two or more A¹groups are identical to each other or different from each other, and thetwo or more Z¹ groups are identical to each other or different from eachother; n² represents 0 or 1; and K¹ represents a structure representedby formula (I-1-a), formula (I-1-b), or formula (I-1-c):

wherein, in formula (I-1-a), formula (I-1-b), and formula (I-1-c), eachof L² and L³ independently represents a single bond, a C₁-C₁₅ linearalkylene group, a C₃-C₁₅ branched alkylene group, a C₁-C₁₅ linearalkyleneoxy group, or a C₃-C₁₅ branched alkyleneoxy group, wherein theC₁-C₁₅ linear alkylene group, the C₃-C₁₅ branched alkylene group, theC₁-C₁₅ linear alkyleneoxy group, or the C₃-C₁₅ branched alkyleneoxygroup is unsubstituted or at least one —CH₂— of the C₁-C₁₅ linearalkylene group, the C₃-C₁₅ branched alkylene group, the C₁-C₁₅ linearalkyleneoxy group, or the C₃-C₁₅ branched alkyleneoxy group issubstituted by —C≡C—, —CH═CH—, —CF₂O—, —SiR^(a) ₂—, —O—, —COO—, —OCO—,or —OOC—, and/or at least one hydrogen atom of the C₁-C₁₅ linearalkylene group, the C₃-C₁₅ branched alkylene group, the C₁-C₁₅ linearalkyleneoxy group, or the C₃-C₁₅ branched alkyleneoxy group issubstituted by a halogen atom, and wherein R^(a) represents a C₁-C₁₀linear alkyl group or a C₃-C₁₀ branched alkyl group, and two R^(a)groups bonded to the same Si atom are identical to each other ordifferent from each other; each of R², R³ and R⁴ independentlyrepresents fluorine, chlorine, hydrogen, a C₁-C₈ linear alkyl group, aC₃-C₈ branched alkyl group, a C₁-C₈ linear alkoxy group, or a C₃-C₈branched alkoxy group, wherein the C₁-C₈ linear alkyl group, the C₃-C₈branched alkyl group, the C₁-C₈ linear alkoxy group, or the C₃-C₈branched alkoxy group is unsubstituted or at least one —CH₂— of theC₁-C₈ linear alkyl group, the C₃-C₈ branched alkyl group, the C₁-C₈linear alkoxy group, or the C₃-C₈ branched alkoxy group is substitutedby —CH═CH—, —CF₂O—, —O—, —COO—, —OCO—, or —OOC—, and/or at least onehydrogen atom of the C₁-C₈ linear alkyl group, the C₃-C₈ branched alkylgroup, the C₁-C₈ linear alkoxy group, or the C₃-C₈ branched alkoxy groupis substituted by a halogen atom; n³+n⁴=3, n⁴ represents 2 or 3, and thetwo or more L² groups are identical to each other or different from eachother, and the two or more X¹ groups are identical to each other ordifferent from each other; n⁵+n⁶=3, n⁶ represents 2 or 3, and the two ormore L² groups are identical to each other or different from each other,and the two or more X² groups are identical to each other or differentfrom each other; each of X¹ and X² independently represents

wherein Y¹ represents —OH, a C₁-C₈ alkyl group, or a C₂-C₈ alkenylgroup, and at least one hydrogen atom of the C₁-C₈ alkyl group or theC₂-C₈ alkenyl group is substituted by —OH; Y² represents hydrogen,halogen, a C₁-C₈ alkyl group, or a C₂-C₈ alkenyl group, wherein theC₁-C₈ alkyl group or the C₂-C₈ alkenyl group is unsubstituted or atleast one hydrogen atom of the C₁-C₈ alkyl group or the C₂-C₈ alkenylgroup is substituted by a halogen atom; K² represents a structurerepresented by formula (I-1-d), formula (I-1-e), or formula (I-1-f):

and K³ represents a structure represented by formula (I-1-g) or formula(I-1-h):

wherein, in formula (I-1-d), formula (I-1-e), formula (I-1-f), formula(I-1-g), and formula (I-1-h), each of L¹, L², L³, L⁴, L⁵, L⁶, and L⁷independently represents a single bond, a C₁-C₁₅ linear alkylene group,a C₃-C₁₅ branched alkylene group, a C₁-C₁₅ linear alkyleneoxy group, ora C₃-C₁₅ branched alkyleneoxy group, wherein the C₁-C₁₅ linear alkylenegroup, the C₃-C₁₅ branched alkylene group, the C₁-C₁₅ linear alkyleneoxygroup, or the C₃-C₁₅ branched alkyleneoxy group is unsubstituted or atleast one —CH₂— of the C₁-C₁₅ linear alkylene group, the C₃-C₁₅ branchedalkylene group, the C₁-C₁₅ linear alkyleneoxy group, or the C₃-C₁₅branched alkyleneoxy group is substituted by —C≡C—, —CH═CH—, —CF₂O—,—SiR^(a) ₂—, —O—, —COO—, —OCO—, or —OOC—, and/or at least one hydrogenatom of the C₁-C₁₅ linear alkylene group, the C₃-C₁₅ branched alkylenegroup, the C₁-C₁₅ linear alkyleneoxy group, or the C₃-C₁₅ branchedalkyleneoxy group is substituted by a halogen atom, and wherein R^(a)represents a C₁-C₁₀ linear alkyl group or a C₃-C₁₀ branched alkyl group,and two R^(a) groups bonded to the same Si atom are identical to eachother or different from each other; each of R², R³, R⁴, R⁵ and R⁶independently represents fluorine, chlorine, hydrogen, a C₁-C₁₀ linearalkyl group, a C₃-C₁₀ branched alkyl group, a C₁-C₁₀ linear alkoxygroup, or a C₃-C₁₀ branched alkoxy group, wherein the C₁-C₁₀ linearalkyl group, the C₃-C₁₀ branched alkyl group, the C₁-C₁₀ linear alkoxygroup, or the C₃-C₁₀ branched alkoxy group is unsubstituted or at leastone —CH₂— of the C₁-C₁₀ linear alkyl group, the C₃-C₁₀ branched alkylgroup, the C₁-C₁₀ linear alkoxy group, or the C₃-C₁₀ branched alkoxygroup is substituted by —C≡C—, —CH═CH—, —CF₂O—, —O—, —COO—, —OCO—, or—OOC—, and/or at least one hydrogen atom of the C₁-C₁₀ linear alkylgroup, the C₃-C₁₀ branched alkyl group, the C₁-C₁₀ linear alkoxy group,or the C₃-C₁₀ branched alkoxy group is substituted by a halogen atom;n⁹+n¹⁰=3, n¹⁰ represents 2 or 3, and the two or more L⁷ groups areidentical to each other or different from each other, and the two ormore X⁴ groups are identical to each other or different from each other;n¹² represents 1, 2, or 3, n¹¹+n¹²=3, and when n¹² represents 2 or 3,the two or more L² groups are identical to each other or different fromeach other, and the two or more X⁵ groups are identical to each other ordifferent from each other; when n¹¹ represents 2, the two R² groups areidentical to each other or different from each other; and n¹⁴ represents1, 2, or 3, n¹³+n¹⁴=3, and when n¹⁴ represents 2 or 3, the two or moreL² groups are identical to each other or different from each other, andthe two or more X⁶ groups are identical to each other or different fromeach other; when n¹³ represents 2, the two R⁴ groups are identical toeach other or different from each other; each of X³, X⁴, X⁵ and X⁶independently represents hydrogen, —OH,

wherein, when K¹ represents the structure represented by formula (I-1-a)or formula (I-1-b), each of X¹ and X² independently represents

and when K¹ represents the structure represented by formula (I-1-c),each of X³, X⁴, X⁵ and X⁶ represents hydrogen or


8. The additive as claimed in claim 7, wherein when an amount of thefirst additive molecule is set to 1 part by weight, an amount of thethird additive molecule is 0.01-80 parts by weight.
 9. A liquid-crystalcomposition, comprising a first component and a second component,wherein the first component comprises at least one additive as claimedin claim 1, and the second component comprises at least one compoundrepresented by formula (II):

wherein each of R²¹ and R²² independently represents hydrogen, halogen,a C₁-C₁₅ alkyl group, or a C₂-C₁₅ alkenyl group, wherein the C₁-C₁₅alkyl group or the C₂-C₁₅ alkenyl group is unsubstituted or at least onehydrogen atom of the C₁-C₁₅ alkyl group or the C₂-C₁₅ alkenyl group issubstituted by a halogen atom, and/or at least one —CH₂— of the C₁-C₁₅alkyl group or the C₂-C₁₅ alkenyl group is substituted by —O—, andwherein the —O— does not directly bond to another —O—; each of B¹, B²,and B³ independently represents a 1,4-phenylene group, a1,4-cyclohexylene group, a benzofuran-2,5-diyl group, a1,3-dioxane-2,5-diyl group, a tetrahydropyran-2,5-diyl group, a divalentdioxabicyclo[2.2.2]octylene group, a divalenttrioxabicyclo[2.2.2]octylene group, a tetrahydronaphthalene-2,6-diylgroup, or an indane-2,5-diyl group, wherein the 1,4-phenylene group, the1,4-cyclohexylene group, the 1,3-dioxane-2,5-diyl group, thebenzofuran-2,5-diyl group, the tetrahydronaphthalene-2,6-diyl group, theindane-2,5-diyl group, or the tetrahydropyran-2,5-diyl group isunsubstituted or at least one hydrogen atom of the 1,4-phenylene group,the 1,4-cyclohexylene group, the 1,3-dioxane-2,5-diyl group, thebenzofuran-2,5-diyl group, the tetrahydronaphthalene-2,6-diyl group, theindane-2,5-diyl group, or the tetrahydropyran-2,5-diyl group issubstituted by a halogen atom or a —CN group, and/or at least one —CH₂—of the 1,4-phenylene group, the 1,4-cyclohexylene group, the1,3-dioxane-2,5-diyl group, the benzofuran-2,5-diyl group, thetetrahydronaphthalene-2,6-diyl group, the indane-2,5-diyl group, or thetetrahydropyran-2,5-diyl group is substituted by —O—, —N— or —S—, andwherein the —O—, —N—, and —S— do not directly bond to one another; eachof Z²¹ and Z²² independently represents a single bond, a C₁-C₄ alkylenegroup, a C₂-C₄ alkenylene group, or a C₂-C₄ alkynylene group, whereinthe C₁-C₄ alkylene group, the C₂-C₄ alkenylene group, or the C₂-C₄alkynylene group is unsubstituted or at least one hydrogen atom of theC₁-C₄ alkylene group, the C₂-C₄ alkenylene group, or the C₂-C₄alkynylene group is substituted by a halogen atom or a —CN group, and/orat least one —CH₂— of the C₁-C₄ alkylene group, the C₂-C₄ alkenylenegroup, or the C₂-C₄ alkynylene group is substituted by —O— or —S—, andwherein the —O— does not directly bond to —O— or —S—, and —S— does notdirectly bond to —S—; and n²¹ represents 0, 1, or 2, and when n²¹represents 2, the two B¹ groups are identical to each other or differentfrom each other.
 10. The liquid-crystal composition as claimed in claim9, wherein the second component comprises at least one compoundrepresented by formula (II-1) or formula (II-2):

wherein the definitions of R²¹, R²², B¹, B², Z²², and n²¹ arerespectively the same as the definitions of R²¹, R²², B¹, B², Z²², andn²¹ defined in claim
 9. 11. The liquid-crystal composition as claimed inclaim 9, wherein when a total weight of the second component is 100parts by weight, the first component is 0.01-10 parts by weight.
 12. Theliquid-crystal composition as claimed in claim 9, further comprising athird component, wherein the third component comprises at least onecompound represented by formula (III), formula (IV), or formula (V):

wherein each of K²¹, K²², K²³, and K²⁴ independently represents hydrogenor a methyl group; each of Z²³ and Z²⁴ independently represents a singlebond, a C₁-C₁₅ linear alkylene group, a C₃-C₁₅ branched alkylene group,a C₂-C₁₅ linear alkenylene group, or a C₃-C₁₅ branched alkenylene group,wherein the C₁-C₁₅ linear alkylene group, the C₃-C₁₅ branched alkylenegroup, the C₂-C₁₅ linear alkenylene group, or the C₃-C₁₅ branchedalkenylene group is unsubstituted or at least one hydrogen atom of theC₁-C₁₅ linear alkylene group, the C₃-C₁₅ branched alkylene group, theC₂-C₁₅ linear alkenylene group, or the C₃-C₁₅ branched alkenylene groupis substituted by a halogen atom, and/or at least one —CH₂— of theC₁-C₁₅ linear alkylene group, the C₃-C₁₅ branched alkylene group, theC₂-C₁₅ linear alkenylene group, or the C₃-C₁₅ branched alkenylene groupis substituted by —O—, —CO—, —COO—, or —OCO—, and wherein the —O—, —CO—,—COO—, and —OCO— do not directly bond to one another; each of Z²⁵, Z²⁶,Z²⁷, and Z²⁸ independently represents a single bond, —C≡C—, a C₁-C₁₅linear alkylene group, a C₃-C₁₅ branched alkylene group, a C₂-C₁₅ linearalkenylene group, or a C₃-C₁₅ branched alkenylene group, wherein theC₁-C₁₅ linear alkylene group, the C₃-C₁₅ branched alkylene group, theC₂-C₁₅ linear alkenylene group, or the C₃-C₁₅ branched alkenylene groupis unsubstituted or at least one hydrogen atom of the C₁-C₁₅ linearalkylene group, the C₃-C₁₅ branched alkylene group, the C₂-C₁₅ linearalkenylene group, or the C₃-C₁₅ branched alkenylene group is substitutedby a halogen atom, and/or at least one —CH₂— of the C₁-C₁₅ linearalkylene group, the C₃-C₁₅ branched alkylene group, the C₂-C₁₅ linearalkenylene group, or the C₃-C₁₅ branched alkenylene group is substitutedby —SiR^(e) ₂—, —S—, —O—, —CO—, —COO—, —OCO—, —CO—NR^(e)—, or—NR^(e)—CO—, and the —SiR^(e) ₂—, —S—, —O—, —CO—, —COO—, —OCO—,—CO—NR^(e)—, and —NR^(e)—CO— do not directly bond to one another,wherein R^(e) represents hydrogen, a C₁-C₄ linear alkyl group, or aC₃-C₄ branched alkyl group, and the two R^(e) groups bonded to the sameSi atom are identical to each other or different from each other; eachof B⁴, B⁵, B⁶ and B⁷ independently represents a 1,4-phenylene group, a1,4-cyclohexylene group, a benzofuran-2,5-diyl group, a1,3-dioxane-2,5-diyl group, a tetrahydropyran-2,5-diyl group, a divalentdioxabicyclo[2.2.2]octylene group, a divalenttrioxabicyclo[2.2.2]octylene group, a tetrahydronaphthalene-2,6-diylgroup, or an indane-2,5-diyl group, wherein the 1,4-phenylene group, the1,4-cyclohexylene group, the benzofuran-2,5-diyl group, the1,3-dioxane-2,5-diyl group, the tetrahydropyran-2,5-diyl group, thedivalent dioxabicyclo[2.2.2]octylene group, the divalenttrioxabicyclo[2.2.2]octylene group, the tetrahydronaphthalene-2,6-diylgroup, or the indane-2,5-diyl group is unsubstituted or is substitutedby at least one substituent, wherein the at least one substituent isselected from fluorine, chlorine, a —CN group, a C₁-C₁₂ linear alkylgroup, a C₃-C₁₂ branched alkyl group, a C₂-C₁₂ linear alkenyl group, aC₂-C₁₂ linear alkynyl group, a C₄-C₁₂ branched alkenyl group, or aC₄-C₁₂ branched alkynyl group, wherein the C₁-C₁₂ linear alkyl group,the C₃-C₁₂ branched alkyl group, the C₂-C₁₂ linear alkenyl group, theC₂-C₁₂ linear alkynyl group, the C₄-C₁₂ branched alkenyl group, or theC₄-C₁₂ branched alkynyl group is unsubstituted or at least one hydrogenatom of the C₁-C₁₂ linear alkyl group, the C₃-C₁₂ branched alkyl group,the C₂-C₁₂ linear alkenyl group, the C₂-C₁₂ linear alkynyl group, theC₄-C₁₂ branched alkenyl group, or the C₄-C₁₂ branched alkynyl group issubstituted by a halogen atom, and/or at least one —CH₂— of the C₁-C₁₂linear alkyl group, the C₃-C₁₂ branched alkyl group, the C₂-C₁₂ linearalkenyl group, the C₂-C₁₂ linear alkynyl group, the C₄-C₁₂ branchedalkenyl group, or the C₄-C₁₂ branched alkynyl group is substituted by—O—, —CO—, —COO—, or —OCO—, and the —O—, —CO—, —COO—, and —OCO— do notdirectly bond to one another; M¹ represents a single bond, —CH₂O—,—OCH₂—, —CH₂CH₂—, —CH═CH—, —C≡C—, —CH₂—, —C(CH₃)₂—, —C(CF₃)₂—, —SiH₂—,—Si(CH₃)₂—, or —Si(CF₃)₂—; each of R²³ and R²⁴ independently representsa C₁-C₃₀ linear alkyl group or a C₃-C₃₀ branched alkyl group, whereinthe C₁-C₃₀ linear alkyl group or the C₃-C₃₀ branched alkyl group isunsubstituted or at least one hydrogen atom of the C₁-C₃₀ linear alkylgroup or the C₃-C₃₀ branched alkyl group is substituted by a halogenatom, and/or at least one —CH₂— of the C₁-C₃₀ linear alkyl group or theC₃-C₃₀ branched alkyl group is substituted by —Si—, —O—, —CO—, —COO—, or—OCO—, and the —Si—, —O—, —CO—, —COO—, and —OCO— do not directly bond toone another; and each of n²² and n²³ independently represents an integerof 0 to 3, and when n²² is 2 or more, the two B⁴ groups are identical toeach other or different from each other, and the two M¹ groups areidentical to each other or different from each other; and when n²³ is 2or more, the two B⁶ groups are identical to each other or different fromeach other, and the two Z²⁷ groups are identical to each other ordifferent from each other.
 13. The liquid-crystal composition as claimedin claim 12, wherein when a total weight of the second component is 100parts by weight, the third component is 0.01-10 parts by weight.
 14. Aliquid-crystal display device comprising: a first substrate; a secondsubstrate disposed opposite to the first substrate; a liquid-crystallayer disposed between the first substrate and the second substrate,wherein the liquid-crystal layer comprises the additive as claimed inclaim 1.